The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish & Wildlife Service. The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited. Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.
To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962. The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years. It is the most widely-recognized conference of its kind worldwide.
Detailed histories of the development of this Conference are found in these publications:
Volume 24, 2010
Vertebrate pest animal control and research is a relatively small area of activity within the agricultural and environmental fields. However, it is critical for agricultural productivity and biodiversity. There is much to be gained by having vertebrate pest controllers and researchers collaborating worldwide. The critical mass achieved through collaboration will result in faster registration of new products, better implementation of new methods, and increased skills within vertebrate pest units. The plain fact is that vertebrate pest control involves the killing of animals, sometimes those with iconic status. Having the public, or even other scientists, recognize the need for animal control can be complicated because of people’s natural concern for the welfare of animals. Those involved in the sector must become better advocates for the agricultural and biodiversity benefits of animal control. Although it is very uncomfortable for many scientists, they must face up to community dialogue in all its modern forms, and not simply rely on scientific reports and published papers speaking for themselves.
Emerging Challenges of Managing Island Invasive Species: Potential Invasive Species Unintentionally Spread from Military Restructuring
The U.S. Department of Defense is in the process of restructuring military assets in the Pacific Basin that includes moving more troops to Guam. As a result of this process, the potential risk of vertebrate invasive species may increase across Micronesia. We identified the pathways through which goods and materials are moved throughout the Pacific basin and then developed a list of the most likely invasive vertebrates that could be moved in these pathways. We reviewed the available literature, interviewed experts, and evaluated pathways according to a fixed set of criteria to determine the risk of the pathway to transport invasive species. Some of the potentially high-risk pathways are military and commercial aircraft and vehicles, mail, shipping containers, and aquaculture. The following are species that may spread or become established in the Pacific without the implementation of measures to reduce risk: brown tree snake, habu, Asian beauty snake, common wolf snake, anole, gecko, coqui frog, cane toad, red-vented bulbul, Indian myna, and Indian mongoose.
Rodent Eradication on Cocos Island, Guam: Integrating Wildlife Damage Management, Resort Operations, and Non-Target Concerns
Introduced Polynesian rats threatened native bird populations and forest habitat on Cocos Island, Guam. To eliminate the threat posed by rat populations, a rodent eradication was conducted on the 33.6-hectare off-shore island in March and April 2009. An integrated approach to eradication was implemented that included trapping, bait stations, and hand broadcast of rodenticide bait. Trapping was conducted within the resort buildings, where human activity precluded the use of rodenticides. Bait stations, employed in commensal resort settings, were designed to prevent terrestrial crabs from accessing the bait. In addition, bait station deployment and retraction methods were used to reduce impacts on daily resort operations. Non-target concerns, primarily with native forest birds during broadcast operations, supported a decision to use diphacinone, a rodenticide with low avian toxicity risk. Bait consumption by the locally threatened Micronesian starling was evident during the broadcast application, but substantial monitoring for non-target impacts revealed no mortality or sublethal effects for starlings or other potential non-targets. Eradication operations on Cocos Island present a prime example of integrated wildlife damage management, combining traditional eradication methods with novel approaches to address site-specific challenges.
Rat Control for the Protection of Endangered Birds, Plants, and Tree Snails on the Island of Oahu, Hawaii
Since 1997, the Oahu Army Natural Resource Program has been controlling rats using diphacinone rodenticide in small-scale bait station grids in combination with rat traps for the protection of one endangered forest bird species, 5 species of endangered Oahu tree snails, and 9 species of endangered plants in 2 mountain ranges on the island of Oahu. Endangered tree snail and some plant populations are protected year-round. Other plants are only protected during their flowering/fruiting season, with small-scale baiting grids in combination with rat traps; and the Oahu Elepaio is only protected during its breeding season, with small-scale bait station grids in combination with rat traps centered on territories. In May 2009, year-round rat control was initiated over a 26-ha forested management unit on Oahu with 440 snap traps. The New Zealand Department of Conservation current best practice rat kill-trapping technology is being utilized for the first time in Hawaii with this large-scale trapping effort. Rat activity within the management unit will be monitored through the use of tracking tunnels. Forest health (seed rain and seedling germination), endangered plant recruitment, endangered tree snail survival, and native invertebrate abundance will be monitored closely to determine the effectiveness of this large-scale trapping effort. The Oahu Army Natural Resource Program is working towards integrating multiple control methods (bait station grids, large-scale rat trap grids, predator-proof fencing, hand and targeted aerial application of rodenticide) over large-scale areas in an effort to determine the most effective means to control rats in Army-managed areas on Oahu.
Effects of Rattus spp. Control Measures and Nesting Substrate on Nest Depredation, East Maui, Hawaii
We monitored natural and artificial nests during a two-part study on East Maui, Hawaii, designed to examine factors influencing nest depredation by black and Polynesian rats. The first half of the study examined the effects of rat control on nest depredation within portions of the Hanawi Natural Area Reserve. Rat density monitoring indicated control efforts had significantly reduced black rat captures in treatment areas, but no differences in survival of artificial or natural nests between treatment and control areas were observed. The second half of the study examined the effect of nesting substrate on nest depredation in the Makawao Forest Reserve during June 2003 and June 2004. We chose fruiting and non-fruiting nest substrates for artificial nests in two habitat types, native ohia/koa forest and an adjoining forest dominated by non-native tropical ash. Results from snap trapping showed that the relative density of black rats was significantly higher in the ohia/koa forest than the tropical ash forest, but plots with more rat captures did not always have higher rates of nest depredation as predicted. Our findings suggest that there is a large degree of variability in nest depredation by Rattus spp., but that rat density, forest type, and nest substrate influence nest depredation rates.
Once established, invasive rodents cause significant impacts to island flora and fauna, including species extinctions. There have been numerous efforts to eradicate invasive rodents from islands worldwide, with many successes. For a number of reasons, many invasive vertebrates have become established in Florida, including several rodent species. We have implemented rodent eradication efforts on two Florida islands. Using the successful eradication strategy developed for Buck Island, U.S. Virgin Islands, we have attempted the eradication of roof rats from Egmont Key off Tampa Bay. We also are attempting to eradicate Gambian giant pouched rats from Grassy Key in the Florida Keys. On Egmont Key, we used a grid of bait stations containing diphacinone rodenticide bait blocks and hand tossing of bait blocks into thickets. On Grassy Key, we used a grid of bait stations containing a zinc phosphide bait along with intensive live-trapping. We discuss the eradication planning, efforts to minimize nontarget animal losses, and follow-up activities. We also discuss some of the difficulties encountered in each of these two different situations.
Fox squirrels are an emerging urban, suburban, and agricultural vertebrate pest in California. They cause a diversity of damage to vegetation and property. Multiple introductions of fox squirrels into California have led to a rapid expansion of their range in the state. Fox squirrels at the University of California, Davis increased from none to an estimated 1,609 between 2001 and 2009. Damage due to the dense population of fox squirrels is increasing. There are several population control options available, but social considerations may limit the viable options to non-lethal methods. This paper provides an overview of the impacts of the introduced fox squirrel in California and on the University of California, Davis campus.
Wildlife management and conservation biology are full of conflict, especially in regard to introduced vertebrates in Hawai`i. At present, there are 17 introduced mammals with established wild populations in Hawai`i, including 6 ruminants, 4 rodents, 3 feral pets, pigs, donkeys, rock wallabies, and mongooses. Disagreement about the reliability of information on the impacts of introduced mammals in Hawai`i is one reason for conflict between stakeholders, which may undermine conservation and management programs. The objective of this research was to assess what science has recorded in regards to the impact of introduced mammals on the native flora, fauna, and ecosystems of the Hawaiian Islands. A literature (peer-reviewed articles, theses, dissertations, and grey literature) search for data on the impact of these species resulted in 156 articles, which were assigned to 1 of 6 categories that describe science’s ‘Level of understanding’ of the impacts of mammals in Hawai`i. The vast majority of the available data (134/156 articles) resulted from basic observations or general exclosure plots. In terms of their impact in Hawai`i, cats (21 articles), black rats (27 articles), and pigs (40 articles) are the most researched and hence best understood species. Very little is known about the impacts of dogs, rabbits, brush-tailed rock wallabies, and donkeys on the flora, fauna, and ecosystems of Hawai`i. Analysis of the dates of publication of articles suggests research may be influenced by the level of controversy surrounding a species.
Feral Goats in the Hawaiian Islands: Understanding the Behavioral Ecology of Nonnative Ungulates with GPS and Remote Sensing Technology
Nonnative feral ungulates have both direct and indirect impacts on native ecosystems. Hawai`i is particularly susceptible to biological invasions, as the islands have evolved in extreme geographic isolation. In this paper we explore the ecological impacts of nonnative feral goats (Capra hircus) in the Hawaiian Islands, including both the current state of knowledge and future research directions to address knowledge gaps. Understanding how invasive vertebrates impact island ecosystems is important as it provides an informed context for developing contemporary solutions to pressing management problems. Current knowledge gaps, such as the behavioral ecology of goats and their impacts on specific plant species and communities, limit the effectiveness of ecological restoration and conservation in Hawai`i. Emerging technologies in wildlife tracking and remote sensing will enable a greatly improved understanding of the behavior and ecological impacts of these nonnative animals in what is already a highly degraded ecosystem.
Feral pigs threaten biodiversity worldwide by altering ecosystem structure and function. The most noticeable effect of pigs on ecosystems is disturbed soil caused by their rooting foraging behaviour, which can impact upon invertebrate populations, nutrient cycles, and plant regeneration. In this study, we assessed the impact of feral pigs on rainforest dynamics in north-eastern Australia by comparing plots where fencing had been used to exclude pigs for 2 and 14 years with unfenced plots at continual risk to pig damage in both the wet and dry seasons. Rainforest dynamics were quantified using a range of earthworm, soil, litter, and plant characteristics, and we used mixed linear models to explain the response of these variables to both plot type and season. Our results show that feral pigs do not have a strong impact on rainforest dynamics. The only significant result was greater litter moisture in the fenced compared to unfenced long-term plots. In contrast, the majority of response variables exhibited significant seasonal differences. For the plot type and season interaction effect, the only significant result was litter biomass in the long-term plots. There was no significant difference between means for the fenced and unfenced plots within the wet and dry seasons; however, litter biomass was greater in the unfenced plots during the wet season and, conversely, greater in the fenced plots during the dry season. Overall, our results show that season has a greater impact on rainforest dynamics than feral pigs.
The risk of non-target species being harmed by pest management activities can be a major impediment to animal control being implemented. This problem is particularly acute in complex faunal communities, where the pest occurs with functionally-similar species. Here, we present a framework for developing target-specific pest management tools for complex communities that helps managers reduce the risk of non-target species impacts. We applied the framework to the problem of poison baiting for feral pig control in the tropical rainforests of north-eastern Australia, and identified several potential methods to reduce adverse baiting impacts on non-target species. We evaluated the target-specificity of different baits and bait presentation methods using camera traps and sandplots to monitor animal-bait interactions in the field. As predicted using the framework, making baits available only at night prevented bait take by diurnal species, and bait burial substantially reduced bait consumption by nonfossorial species. The illumination of bait sites also reduced the foraging intensity of small non-target mammals, without inhibiting bait take by feral pigs. Two putative auditory repellents for small mammals were ineffective. Temporal variation in bait take by pigs and other species was unpredictable, and we were unable to exploit seasonally-variable factors to further enhance targetspecificity. The use of a starch-rich vegetable bait, rather than an omnivore bait, prevented bait take by dingoes and improved bait take by feral pigs. The use of a light plastic container to cover this bait prevented bait take by small omnivores when an uncovered free-feed was also provided. This latter baiting method renders nocturnal distribution, bait burial, and site illumination unnecessary, and provides a simple, target-specific baiting protocol that will allow effective feral pig control in the region for the first time. Our field results demonstrate the usefulness of the framework in our study site. The framework is similarly suitable for developing target-specific methods for delivering other chemical or biological agents to wildlife or pest populations, or for developing other pest control tools such as traps. The framework awaits further evaluation in other complex faunal communities.
The 2008 - 2009 Aerial Feral Pig and Feral Goat Shooting Program: A Case Study in Northern New South Wales, Australia
The 2008-2009 Aerial Feral Pig and Feral Goat Shooting Program aimed to reduce feral mammal infestations in the Barnard/Hunter River catchment areas, northern New South Wales (NSW), Australia, over a 2-year period, as well as to provide skills to landholders to manage vertebrate pests. By accomplishing these reductions in pest animal densities, it endeavoured to reduce impacts of feral mammals on soil and water resources and on native flora and fauna, thereby protecting ecosystems and giving benefits to the wider community. The NSW Department of Industries and Energy identified the control area, including the Barnard and Hunter River catchment areas, as having one of the highest populations of feral pigs in northern NSW. The area contains diverse and vulnerable ecosystems of woodlands, remnant rainforest, escarpment, and open grazing areas. Projects were designed to use best practice pest animal management methods, including aerial shooting, followed by a trapping campaign and ground shooting. Stakeholders included NSW National Parks and Wildlife Service, Armidale and Hunter Rural Lands Protection Boards, and up to 336 private landowners. Aerial shooting was undertaken in July, because winter is the most opportune season for this method. In 2008, a total of 913 feral pigs, 650 feral goats, 18 deer, and 4 wild dogs were destroyed. In 2009, 1,338 feral pigs, 900 feral goats, and 336 deer were destroyed, all of which were primary target animals. Trapping and poisoning were used to control feral pigs and an extensive ground-shooting program was put in place to control feral goats and the emerging deer problem. Monitoring of residual populations, through New England Livestock Health and Pest Authority property inspections, and assessment of damage caused by feral animals were undertaken at the conclusion of both projects. Ground trapping continues over a 4-month period, and ground shooting is ongoing and opportunistic.
The Hawaiian Islands’ first predator exclusion fence project is planned for spring 2010 at the Ka`ena Point Natural Area Reserve, on the Island of Oahu. The Reserve hosts one of the largest seabird colonies in the main Hawaiian Islands and is home to threatened and endangered Hawaiian plants. Both avian and plant species in the Reserve are impacted by non-native mammalian predators. Although predator control operations have been ongoing for over a decade, predator ingress into the Reserve is continual and results in the annual loss of up to 15% of fledgling seabirds. It is projected that the planned predator exclusion fence and subsequent mammal removal will be more cost effective and provide an impervious means of keeping mammalian predators out of the Reserve, thus preserving and improving critical habitat. Because non-native mammalian predators cause biological damage to many of Hawai`i’s fragile avian and plant species in almost every ecosystem island-wide, this project will lead the way in further developing a new management strategy for the protection and preservation of island ecosystems.
The effects of feral cats on Pacific island ecosystems are a well known and long standing pest problem. While control and/or eradication of feral cat populations have been successfully accomplished on several islands, they are typically in locations with little to no human population. The Hawaiian Islands have a human population of just over 1.2 million people, making certain feral cat control methods difficult, if not impossible, to implement. The University of Hawai`i at Mānoa, located in Honolulu, has a large number of feral cats living on it that often cause problems among the numerous stakeholders who use or frequent the campus. One of the primary concerns related to the cats is their feces, which may carry such diseases as toxoplasmosis and may cause illness in the employees that have to clean up after the cats. The university has implemented the use of feeding stations and litter boxes to obtain a population estimate and control the quantity of cat feces on the ground. But these two approaches have not been successful, due to inconsistent participation by the cat colony caretakers. Hence, little information exists about the status of the campus’s feral cat population. In order to begin addressing the campus cat problem, our goal is to develop a survey method for estimating the distribution and size of cat colonies, conduct health assessments, and identify ownership of cats with microchips. We are conducting surveys to estimate the population size, to see if it changes over time, and to determine basic health indices of the cats. Ultimately, we expect to provide information on whether the feral cat population is changing over time and whether or not trap-neuter-release efforts are succeeding and reducing the population relative to removal, and status quo management options.
Feral cats are considered one of the most detrimental invasive species within island ecosystems. Non-native feral cats have been on San Nicolas Island (5,896 ha, or 14,562 acres) since at least 1952. In an effort to counter the negative impacts of feral cats on marine and terrestrial birds, the San Nicolas seabird restoration project, with the goal of eradicating cats, was initiated in June 2009. Although aimed at seabird restoration, feral cat eradication is expected to aid in the protection of endemic terrestrial species, including the federally threatened island night lizard, federally threatened western snowy plover, a subspecies of deer mouse, and the state threatened island fox. Methods including the use of altered padded leg-hold live traps, detection dogs, and hunting are being utilized to deliver a successful eradication within a short window of opportunity. In addition, a trap monitoring system, operated in tandem with field PCs and GIS, has proven effective in managing large numbers of traps. Since initiation, a rotation of staff has provided an average of 6 field personnel on-island at any one time to staff the project continuously over 10 months. Eradication was complicated by the similarly sized island fox, rugged topography, restricted access to parts of the island by Navy activities, marine mammal presence on the beaches, and sea and shore birds nesting and roosting. Island eradications require multiple methods to effectively remove all cats, and operations on larger islands benefit from the intensive use of management tools such as GIS. The systems developed on the San Nicolas Seabird Restoration Project will advance the global effort to reduce the threats of invasive species, particularly feral cats.
A Trap Monitoring System to Enhance Efficiency of Feral Cat Eradication and Minimize Adverse Effects on Non-Target Endemic Species on San Nicolas Island
Feral cats have significant negative impacts on island ecosystems and are a major threat to resident seabird populations. In an attempt to restore populations of Brandt’s Cormorants, western gulls, and other native species on San Nicolas Island, California, feral cats were targeted for eradication. In over 83 successful feral cat eradications from islands, removal by padded leg-hold traps was the most commonly used eradication technique. However, the size of San Nicolas, 5,896 ha (14,562 acres) and the presence of >600 diminutive (average 1.7 kg) endemic island fox presented challenges. A telemetry-based trap monitoring system was developed to remotely check trap status, decrease staff time spent checking traps, and decrease response time to captured animals to limit fox injuries and mortalities due to exposure. This system enabled a team of 6 staff to maintain daily checks of approximately 250 traps and have a response time to captures of <60 minutes during daylight hours. Field staff were trained to assess fox health in the field, and a mobile veterinary hospital was established on island to treat any injuries. The trap monitoring system was composed of transmitter units connected to traps, an island-wide repeater system, a GIS database with field PDA data collection, and a user interface hosted on a local internet network. When activated, each transmitter sent a trapspecific ID code every 4 hours, indicating it was operational. When sprung, a modified ID code was transmitted every 30 minutes until the trap transmitter was reset. Repeaters relayed trap status data, both to a dedicated PC where a set of scripts filtered the raw data to find capture events, and simultaneously to the internet. A web-based software user interface was designed to combine capture events with location information from a GIS database, allowing field staff to quickly identify which traps were sprung and plan the most effective route between all sprung traps. Ultimately, this system was a powerful adaptive management tool that increased staff efficiency and minimized effects on non-target species.
American Bullfrogs as Invasive Species: A Review of the Introduction, Subsequent Problems, Management Options, and Future Directions
Native to the eastern United States, American bullfrogs have been introduced throughout the western U.S. and to several other countries and islands around the world. Bullfrogs are well adapted for many of the permanent water sources that occur within the U.S., and once introduced, they typically become dominant. Because of their large size and voracious appetite, bullfrogs outcompete and prey upon many indigenous species. They are hypothesized to be cause significant negative impacts, which may contribute to the endangerment and extinction of some sensitive species. There are few, if any, effective and efficient control methods to manage invasive bullfrogs. Current methods such as hand or net capture, shooting, and gigging can be labor intensive and often fail to reduce bullfrog numbers. Draining wetland habitats and broadcasting toxicants have severe negative effects on non-target species. New management options, such as locally-sprayed toxicants and multiple-capture traps, could be useful for reducing populations of invasive bullfrogs. However, researchers should make certain that non-target species are not affected by these management techniques.
From the Sea of Cortez to the Aleutian Islands, Alaska: General Principles Applied to Eradication Planning, Compliance, and Implementation (Abstract)
The removal of introduced rodents from islands can be a highly successful, and thus, important conservation tool for land managers. Non-native rodents have adverse impacts to island ecosystems. Rats alone have been implicated in approximately 40-60% of all bird and reptile extinctions globally. Introduced rodents have been removed from more than 330 islands worldwide using techniques adapted over a ~30-year time period – the use of a bait containing a rodenticide delivered by hand into bait stations or broadcast by hand or helicopter, or a combination of these techniques. Island Conservation has applied this basic approach to remove rodents from islands spanning from the deep tropics to north temperate/sub-Arctic latitudes. Across these regions, the same principle has been applied but the details customized to the local biological and sociopolitical environment. The fundamental considerations during rodent eradication planning have included: 1) delivery of a bait containing a rodenticide into every potential rat territory; 2) delivery at a time of year when the rodent population is food stressed and more likely to eat the bait; 3) minimizing or eliminating, wherever possible, risk to non-target species prone to disturbance and/or toxicant exposure; and 4) ensuring appropriate legal or regulatory compliance and acceptance by local communities. In most cases, the balance between the probability of eradication success and these considerations, particularly risk to non-target species and safe workplace seasonal time periods, are not compatible and may conflict. Thus, adjustments to the eradication plans are sometimes necessary, and are done with careful evaluation of counter-risks to eradication efficacy, non-target species, logistics, or workplace safety. We will use our projects as case studies to demonstrate the approach we take to balance the risks and mitigation, with decisions made in conjunction with our project partners. Comprehensive and transparent planning, with the involvement of experts in the eradication field, land managers, local biologists, regulators, and local community are imperative to overall project success.
Trends in Vertebrate Pesticide Use and New Developments: New Zealand Initiatives and International Implications
In New Zealand, sodium fluoroacetate (1080) has been used for vertebrate pest control for several decades. Since the 1990s, some 1080 users have switched to brodifacoum for possum and rodent control because of its ready availability and ease of use. An awareness that field use of brodifacoum results in persistent residues provides the impetus to develop alternatives and provide new tools and greater flexibility. Looking to the future, we seek toxins which increasingly combine “low-residue” characteristics with humaneness, and more selective bait and delivery systems enabling better and more acceptable control of possums, wallabies, mustelids, rodents, feral cats, and rabbits. Experience gained in the 1990s with the introduction of cholecalciferol (Feracol®) and a cyanide pellet (Feratox®), which both kill possums without secondary poisoning, underpins the extension in 2009 of the Feratox® registration to include introduced Dama wallabies. To date, zinc phosphide has not been registered in NZ, despite its field use in Australia and the U.S. and low secondary poisoning risk compared with 1080. Research and registration dossiers are being assessed in 2009-10 for zinc phosphide containing products for possum and rodent control. Registration documents are also being prepared for a combination of cholecalciferol and coumatetralyl to provide a slow-acting alternative to brodifacoum for the field control of possums, rodents, and rabbits with low risk of bio-accumulation. Anticipated timelines for product availability are 2010 (zinc phosphide) and 2011-13 (cholecalciferol and coumatetralyl). Our intention now is to move beyond these conventional rodenticides and develop new vertebrate pesticides. For example, we are pursuing the registration of para-aminopropiophenone (PAPP) for humane control of stoats and feral cats, and a series of related novel toxins and other compounds that target the red blood cell for other pest species including rodents. PAPP products should be available in 2010, subject to registration approvals. New research initiatives in 2010 will increasingly result in a shift in focus to the development of novel rodenticides aided by new international research collaborations.
Alternatives to 1080 Poison for Control of Native Animals in Tasmania: A Response to Public Concerns
Compound 1080 (sodium monofluoroacetate) has been used in Tasmania for control of introduced rabbits since the early 1950s and for the native Bennett’s wallaby, Tasmanian pademelon, and brushtail possum for almost as long. Recently, public pressure has resulted in a target to phase out the use of 1080 by 2015. In 2005, the Australian and Tasmanian Governments announced funding for a program to assist in the development of alternatives to 1080. Following an initial independent review in 2006, research and demonstrations focussed on fencing and barriers; shooting, trapping and behavioural research; alternative toxins and delivery mechanisms; repellents; and damage / control relationships. The most positive outcomes from the program were increased understanding of the complexity of the Tasmanian browsing damage problem and the need to measure and address the damage, rather than count the numbers of animals culled. For those agricultural producers who had used it, wallaby-proof fencing was thought to be the most effective long-term control option, despite the increased costs of materials and maintenance. Fencing is not suitable for all situations, including most forest production areas; it is not a stand-alone control option, as it must be accompanied by culling at construction and over time. Shooting is the second-most-important method of control, and there is scope for improvements in effectiveness through better practices and equipment. Trapping can be useful in some areas but it is expensive, and current traps will not catch Bennett’s wallabies. Repellents have not proven to be effective, and further developmental work is required before Feratox® can be recommended for safe use in Tasmania.
Uptake of the Vertebrate Pesticide 1080 (Sodium Fluoroacetate) by Watercress, a Culturally Important Food Plant
A field-based experiment was carried out to determine if watercress, commonly harvested by Māori, the indigenous people of New Zealand, could take up the vertebrate pesticide sodium fluoroacetate (Compound 1080), often applied aerially in New Zealand for the control of introduced vertebrate pests. Single toxic baits were placed within seven watercress stands, while three stands received non-toxic controls. Water and plant tissue samples were taken out to 17 days after bait placement, and samples analysed for 1080 content. 1080 was recorded from treatment watercress samples, with a maximum concentration of 63 ppb recorded on Day 7. Subsequent sampling did not show any 1080 in watercress tissue. It is concluded that there is a negligible secondary poisoning risk to humans via consumption of watercress after exposure to 1080.
There is a need in New Zealand for a new, more advanced generation of toxins to minimize the impact of invasive animals. A new pest control agent, para-aminopropiophenone (PAPP), represents a lead candidate presently undergoing registration for the humane control of stoats and feral cats. It exhibits low toxicity to most bird species, no secondary poisoning risk, and has a simple and highly effective antidote. PAPP induces methemoglobinemia (MtHb), which acts to prevent oxygen from binding to red blood cells. This reduces oxygen supply to the brain, causing animals to become lethargic, sleepy, and unconscious prior to eventual death in 1 to 2 hours. Despite such promise, to date no previous study has comprehensively examined the effect of modifying the structure of PAPP on MtHb induction. Using PAPP as a platform, this paper describes the design, synthesis, and bioevaluation of PAPP-like red blood cell toxins. The impacts of introducing groups of varying electronic nature at different positions on the PAPP molecule are presently being evaluated. Analogues are synthesized and their MtHb-inducing properties determined using an in vitro assay to establish a formal structure-activity profile. In vivo evaluation in rats is used to assess both their acute toxicity and humaneness of potential candidates. Structure-activity profiles are discussed with the objective of optimizing the bioavailability and potency of PAPP-like compounds to target, high priority pests, particularly rodents.
Para-aminopropiophenone (PAPP) Research, Development, Registration, and Application for Humane Predator Control in New Zealand
Feral cat and stoat control is conducted in New Zealand to protect a number of threatened native species, including kiwi, from predation. Para-aminopropiophenone (PAPP) is being developed for predator control. Previously reported cage trials have shown PAPP presented in a meat bait was palatable and effective, while symptoms observed demonstrated PAPP to be humane. Subsequent field trials on stoats were undertaken in two blocks of native forest and achieved 83% and 87% reductions in the stoat abundance index, and a field trial on a population of radio-collared feral cats had an 84% kill. PAPP represents one compound from a new class of active ingredients, which we are calling red blood cell toxins. These vertebrate pesticides have humaneness, and low secondary and non-target poisoning risks, as their primary consideration. The dose is optimised to be effective in the field and reduces oxygen supply to the brain such that animals become lethargic, sleepy and unconscious prior to death within 1-2 hours. Results from these field trials on stoats and feral cats indicate that PAPP will be a useful additional tool for predator control.
Compound 1080 has been used to control native wallabies and possums in Tasmania for over 50 years. Public concern in relation to humaneness and its effects on domestic dogs and nontarget species has led to opposition to its use. Feratox®, a form of encapsulated cyanide pellet registered for brushtail possum control in New Zealand, was considered as a replacement toxin. Trials in New Zealand showed that the material is fast-acting and humane in wallabies. In Tasmania, protocols were developed using bait stations that would minimise access by nontarget macropods and wombats. In field trials using Feratox®, however, there was excessive spillage of toxic pellets and variation in bait take between seasons by Tasmanian pademelons. Further work is under way to resolve these issues to see if protocols can be developed for the safe and effective use of cyanide pellets in areas where nontarget mammals are prevalent.
Strychnine has recently been made available in Canada under an emergency registration program for the control of Richardson’s ground squirrels. From 2007 to 2009, we tested the control efficacy of this poison using >1-year-old and newly produced strychnine on hulless oats, canary seed, and alfalfa pellets. Newly produced 2% liquid strychnine, mixed with hulless oats to formulate 0.4% strychnine freshly mixed baits, controlled ≥70% of adult and juvenile ground squirrels in spring and summer. Other types of strychnine baits were not as reliable from one season to the other. At 0.2% concentration, strychnine-treated oats were relatively inefficient. When >1 year old, the control efficacy of strychnine baits dropped significantly. Independent of the age of the product, strychnine killed non-target animals. This paper recommends a series of measures to ensure quality control and greater selectivity.
Fumigation of California Ground Squirrels Revisited: Are Fumigants an Effective Method for Controlling Ground Squirrels?
Fumigation with either gas cartridges or aluminum phosphide is often considered to be an effective method for controlling California ground squirrel populations, although few studies have corroborated their effectiveness. Additionally, utilizing aluminum phosphide in combination with gas cartridges could increase effectiveness of both fumigants by indicating additional burrow openings through escaping smoke from gas cartridges and allowing for treatment of these additional openings with aluminum phosphide, which is a cheaper and potentially more effective material. Therefore, we compared the efficacy of gas cartridges, aluminum phosphide, and a combined treatment on ground squirrel populations from mid-April through early May 2009 to determine which was most effective. We established 4 plots (3 treatments plus control) at each of 2 treatment sites in Madera County, California. All plots were between 1 and 2 ha in size with survey areas of 0.3 - 0.5 ha centrally located within the plot. Ground squirrels were visually counted within survey areas for 3 consecutive days prior to treatment. Following counting, treatments were applied. Forty-eight hours post-treatment, squirrels were again counted within survey areas to determine percent control. These counts were repeated the following 2 days. All treatments were then reapplied for the same plots, with similar surveys again following 48 hours post-treatment. We found that all fumigation methods resulted in marginal to exceptional control of ground squirrels (percent control: gas cartridges = 62 - 86%, aluminum phosphide = 97 - 100%, gas cartridges + aluminum phosphide = 59 - 71%). We suggest aluminum phosphide use could be expanded to increase ground squirrel control in California, given its high efficacy combined with its relatively cheap material cost.
Nontarget Risk and Environmental Fate of the Broadcast Application of a Diphacinone Rodenticide at Mōkapu and Lehua Islands, Hawai'i
Invasive commensal rodents such as Rattus spp. and Mus spp. imperil many threatened and endangered native species including plants, invertebrates and birds within Hawai'i and U.S. territories and possessions in the Pacific. In some cases, the eradication or control of invasive rodents could allow natural recovery and active restoration of native species and ecosystems negatively impacted. The broad scale application of rodenticides is a necessary management tool for this purpose, but it is highly controversial to the public and regulatory agencies. There is great perceived and actual risk of nontarget mortality and environmental contamination. One of the conservation uses of rodenticides registered in Hawai'i is the aerial broadcast of rodenticide bait over large areas of native ecosystems on the main Hawai'ian islands, repeated periodically to maintain reduced rodent population levels. Recognizing that the success of this program depends on public and regulatory support, a coalition of state and federal agencies and private landowners have carefully designed Hawai'i’s rodent control program to minimize short- and longterm environmental impacts. In the early 1990s, diphacinone was selected as the primary rodenticide for conservation uses in Hawai'i because of its long track record of safe and effective use in agriculture worldwide. Hawai'i’s program has 5 components: research on efficacy and environmental impacts, regulatory compliance, developing and using local technical expertise, monitoring of rodenticide impacts and native species recovery and public outreach and engagement, particularly at the community level. After many years of generating the efficacy and safety data in support of regulatory approval by the U.S. Environmental Protection Agency (EPA) and the State of Hawai'i, a diphacinone product (Diphacinone–50, Hacco, Inc., Randolph, WI) was approved in 2007 for conservation uses in the U.S. Subsequently, rodenticide pellets containing the active ingredient diphacinone at 0.005% (50 ppm) were broadcast by helicopter in February 2008 on Mōkapu and in January 2009 on Lehua. Mōkapu was the first island in the world where the aerial broadcast of this less hazardous active ingredient was used to eradicate rats. Island eradications in other parts of the world have usually used broad-spectrum active ingredients that are far more persistent and bioaccumulative, thus imparting a much higher risk to nontarget species and the environment. Monitoring of nontarget and environmental effects on Mōkapu and Lehua did not detect diphacinone residues. A number of factors, including state of Hawai'i restrictions on bait entering the ocean, led to rats surviving on Lehua. These projects demonstrate that the aerial broadcast of a rodenticide containing diphacinone can be an effective and safer tool for conservation. Hawai'i is using the results from Mōkapu and Lehua to plan future rat eradication and control projects and continue development of a long-term program.
Comparative Toxicity of Diphacinone to Northern Bobwhite (Colinus virginianus) and American Kestrels (Falco sparverius)
The acute oral toxicity of the anticoagulant rodenticide diphacinone was found to be about 20 times greater to American kestrels (LD50=97 mg/kg) than to northern bobwhite (LD50=2,014 mg/kg). Several precise and sensitive clotting assays (prothrombin time, Russell’s Viper venom time, thrombin clotting time) were adapted for use in these species, and this combination of assays is recommended to detect effects of diphacinone and other rodenticides on coagulation. Oral administration of diphacinone over a range of doses (sublethal to the extrapolated LD15) prolonged prothrombin time and Russell’s Viper venom time within 24 to 48 hrs post-exposure. Prolongation of in vitro clotting time reflects impaired coagulation complex activity and was detected before or at the onset of overt signs of toxicity and lethality. These data will assist in the development of a pharmacodynamic model to assess and predict rodenticide toxicity to non-target avian species.
Anticoagulant Residual Concentration and Poisoning in Birds Following a Large-Scale Aerial Application of 25 ppm Brodifacoum Bait for Rat Eradication on Rat Island, Alaska
To eradicate invasive Norway rats, an aerial broadcast of the rodenticide Brodifacoum-25W Conservation was conducted on 2,777-ha Rat Island, within the Aleutian Islands Unit of Alaska Maritime National Wildlife Refuge, between 29 September and 5 October 2008. During subsequent visits to Rat Island (in spring and fall 2009) to check for evidence of remaining rats and to look for evidence of nontarget mortality, personnel found an unexpectedly high number of dead birds: more than 420 carcasses, mostly glaucous-winged gulls and bald eagles, but also included 24 other species. Some carcasses had tissue suitable for analysis and were collected. Seventy bird carcasses were necropsied and cause of death was determined for 50 birds; 45 died of brodifacoum toxicosis. Necropsy determined almost all gulls and eagles had extensive hemorrhaging, consistent with brodifacoum poisoning. All eagles and all but 1 gull tested positive for brodifacoum residues. Positive tests for brodifacoum also were recorded for single specimens of emperor goose, northern fulmar, pelagic cormorant, peregrine falcon, rock sandpiper, and gray-crowned rosy finch. Two Lapland longspurs tested positive for exposure to brodifacoum. Nontarget bird mortality from brodifacoum exposure at Rat Island was higher than predicted in the Environmental Assessment.
Environmental Monitoring for Brodifacoum Residues after Aerial Application of Baits for Rodent Eradication
Aerial application of brodifacoum bait for eradication of invasive rodents from islands raises concerns about environmental contamination and adverse effects on nontarget wildlife. We summarize results of environmental monitoring for brodifacoum residues after New Zealand eradications in a fenced reserve at Maungatautari and on the offshore islands Little Barrier, Rangitoto, and Motutapu. Brodifacoum was not detected in extensive freshwater monitoring at Maungatautari, or in freshwater samples from Little Barrier Island. Residual concentrations were present in soil samples from underneath degrading bait pellets on Little Barrier, and decreased to near the limit of detection by c. 100 days after application. No brodifacoum was present in marine shellfish sampled from Little Barrier, Rangitoto or Motutapu. A range of birds, including a kiwi from Little Barrier, were considered nontarget mortalities. Nine little blue penguins found dead on beaches outside the Rangitoto/Motutapu area after baiting were considered most likely to have died of starvation, despite the detection of brodifacoum in three birds. This result highlights the critical role of post-application environmental monitoring in rodent eradications, and information gaps regarding the movement, persistence, and effects of brodifacoum in the environment.
Anticoagulant Residues in Non-Target Wildlife – Assessing Sublethal Exposure to Brodifacoum without Lethal Sampling
Residues of brodifacoum and other second-generation anticoagulant rodenticides are reported worldwide in a range of non-target wildlife, especially predatory or scavenging birds and mammals. Determination of exposure to brodifacoum in such cases relies on analysis of liver tissue. This limits current monitoring efforts to either destructive sampling of live birds or mammals to obtain liver, but more commonly opportunistic post-mortem liver sampling from carcasses in suitable condition. Also, detection of brodifacoum in liver often cannot be confirmed as a contributor to mortality, and within a potential ‘sublethal’ concentration range the toxicological significance of its presence is uncertain. We sought to determine whether dried blood spot (DBS) sampling could form the basis of a non-lethal, minimally invasive method for determining sublethal exposure to brodifacoum in live birds. Validation of a method for detecting brodifacoum in DBS samples, and preliminary comparison of brodifacoum concentrations in DBS and plasma samples, are described.
New Zealand’s Use of Brodifacoum in Eradication Efforts and Current Investigation of New Baits and Toxins
Rodent eradication on islands has transitioned over 30 years in New Zealand through stages of initial scepticism, to early accidental and experimental successes, and now to the current bold large-scale aerial applications over increasingly large and complex island ecosystems. Starting in the 1970s and 1980s, gaining momentum in the 1990s, and continuing to the present day, islands once occupied by rodents are now being reclaimed. Until the mid 1980s, very few islands were entirely free of animal pests. Rodent eradication on islands, using bait in stations and baits applied from the air, has been spectacularly successful. To date, more than 90 islands around New Zealand have been cleared of rodents, and brodifacoum use has had an obvious benefit on valuable island ecosystems. The tactical use of toxic bait to protect island populations of indigenous birds, reptiles, and invertebrates endangered by rats and mice continues to be refined to enable larger and more complex islands to be cleared of rodents. New bait types that are especially attractive to mice as well as rats, long-life baits, new toxins, and tunnel delivery systems will augment existing bait types to aid future eradication programmes and help prevent re-invasions. New developments will need to be ethically and socially acceptable and demonstrate clear advantages in non-target impact as well as efficacy in achieving eradication. These endeavours are part of global efforts to eradicate invasives and manage islands to protect native birds and other important fauna and flora.
In 2008, approximately 70 Canada geese were recovered dead in the Moro Cojo Slough area of Monterey County, California. Birds were necropsied and showed signs of abnormal internal bleeding. A total of 37 livers were analyzed for anticoagulants and 36 of these livers contained chlorophacinone. Death was attributable to chlorophacinone poisoning. Two turkey vultures and a barn owl also died, probably as a result of secondary chlorophacinone poisoning. The source of the chlorophacinone was not obvious, as chlorophacinone is used in several different forms on many different crops and also in commensal use. In addition, there often are several days between exposure and death, allowing the movement of the animal from the site of exposure. The ensuing investigations, which lasted several months, suggested that the exposure was due to expanded use of chlorophacinone pellets on artichokes used to control California voles. Subsequently, the label of the rodenticide product was modified to restrict its use when conditions favor goose presence in artichoke fields. No deaths have occurred since the label modification.
Prairie Dogs, Pesticides, and Protected Species: Concerns for Anticoagulant Use in a Sensitive Ecosystem
The black-tailed prairie dog occupies an estimated 2.4 million acres in the western U.S and is considered to be a keystone species of the Great Plains due to its influence on biological diversity and ecosystem function. Over 200 vertebrate species are known to associate with prairie dog colonies, and there is documentation that at least 9 species exhibit dependence on prairie dogs either for habitat and shelter or as a prey species. Unlike many other burrowing mammals, the prairie dog relies on an open burrow system that results in a significant amount of time spent above ground, rendering them more easily accessible to predatory species. Many species that use the prairie dog as a food source are protected under the Endangered Species Act, the Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act, and include the black-footed ferret, both species of eagle, and several species of raptors. The registration and use of the anticoagulant rodenticides chlorophacinone and diphacinone for prairie dog control presents risks to these protected species due to the potential for secondary poisoning. Anticoagulant rodenticides have caused secondary poisoning in laboratory studies and have been responsible for mortality incidents in the field. Since geographically limited registrations began in 2005, a limited number of such incidents associated with prairie dog control have been documented, and these elicit concern for the more widespread use of these rodenticides that would accompany registrations covering the entire range of the black-tailed prairie dog.
Efficacy of Oat and Pellet Anticoagulant Baits Following Treatment with Oat and Pellet Zinc Phosphide Baits: Implications for Secondary Hazard Management
This study was undertaken to demonstrate the efficacy of oat and pellet type anticoagulant baits (0.01% diphacinone) when used following an initial treatment of 2% zinc phosphide oat and pellet type baits for controlling California ground squirrels. Both broadcast oat and pellet anticoagulant treatments following zinc phosphide treatments resulted in apparently good control, although the power of our pellet tests was not strong because of failure in the control plots. Anticoagulant bait use, on a per acre basis, was well below the allowed application rate (10 lbs/acre) because it was applied only where active ground squirrel burrows remained after controlling the entire population with zinc phosphide. No non-target species were found affected by the zinc phosphide or anticoagulant treatments. As a baiting strategy, the combination of zinc phosphide combined with the subsequent selective application of anticoagulant baits was successful. This approach will likely lead to significantly fewer squirrel carcasses with anticoagulant residues, since most are killed with zinc phosphide and subsequently do not pose a significant secondary risk to predators, scavengers, or pets. This baiting strategy has the potential to significantly reduce secondary hazards from ground squirrel baiting.
Vertebrate Integrated Pest Management programs are designed to utilize the most efficient, environmentally sound control methods, including anticoagulant rodenticides. The anticoagulant rodenticides are efficacious and relatively easy to handle, however there are concerns regarding the risks associated with rodenticides to human health and the environment. The United States Environmental Protection Agency (EPA) issued the Rodenticide Cluster Reregistration Eligibility Decision (RED) in July 1998 in response to the concerns associated with rodenticides. EPA and its stakeholders worked for 10 years developing risk assessments and mitigation plans, issuing the final Risk Mitigation Decision (RMD) on May 28, 2008. The RMD restricts retail sale of second generation anticoagulant rodenticides for commensal use, and it refers field use rodenticide registrants back to the RED, which makes those products Restricted Use. This means that all uses of field use products must be made by a certified applicator. These changes have potentially large ramifications for smaller private applicators that are generally not certified to use Restricted Use materials. The California Department of Food and Agriculture and the University of California Cooperative Extension are working collaboratively to develop curriculum to streamline the exam process for private applicators; however, there is no guarantee that this will be accepted by the Department of Pesticide Regulation.
The Use of Liver Microsome In-Vitro Methods to Study Toxicant Metabolism and Predict Species Efficacy
Liver microsomes are used extensively in human pharmaceutical development to study the metabolism of compounds of interest; however, they are rarely part of the development of toxicants for the control of wildlife. Liver microsome samples from wildlife of interest would likely be harvested in the field without access to laboratory perfusion equipment. Therefore, the metabolic activity of microsomes from perfused and non-perfused livers was compared. There was no significant difference in diphacinone metabolism by liver microsomes from both perfused and non-perfused Wistar rat livers, although chlorophacinone metabolism was significantly different. There are often significant differences in metabolism between species that can be utilized to increase toxicant specificity. In this study bobwhite quail liver microsomes metabolized more diphacinone and chlorophacinone than both Wistar and brown rats. This information can be used during toxicant development to help determine the most sensitive species to toxicants of interest. Additionally, the effect of incubation time on toxicant metabolism was examined to determine optimal experimental conditions. The data from these experiments support the use of liver microsomes as a tool to be used during toxicant development to provide information that can be incorporated into whole animal studies.
This study was designed to give us a better understanding of the relationship between agricultural anticoagulant rodenticide uses and related occurrence of these materials in raptor tissues. The project utilized data from raptor carcasses collected, both in urban San Diego County and in largely agricultural Fresno, Kern, and Madera Counties, as part of the public health surveillance programs of the County Veterinarian(s) and/or Departments of Environmental Health. Most raptors contained detectible levels of second-generation anticoagulants, which are registered only for commensal rodent control in and around structures; very few contained first-generation anticoagulants, which are the only anticoagulants registered for use in agricultural production in California. This suggests that secondary hazards to raptors and other wildlife from anticoagulants stems primarily from retail sale of commensal rodent baits, particularly in residential areas, and not from anticoagulant rodenticide uses in agricultural regions.
On November 27, 2006 the U.S. Environmental Protection Agency (EPA) issued a final rule clarifying two specific circumstances in which a Clean Water Act (CWA) permit is not required to apply pesticides to or around water. They are: 1) the application of pesticides directly to water to control pests, and 2) the application of pesticides to control pests that are present over or near water, where a portion of the pesticides will unavoidably be deposited to the water to target the pests. On January 7, 2009, the U.S. 6th Circuit Court of Appeals held in National Cotton Council et al. v. EPA that the final rule was not a reasonable interpretation of the CWA and vacated the rule. The 6th Circuit held that CWA permits are required for all biological pesticide applications and chemical pesticide applications that leave a residue in water, when such applications are made in or over, including near, waters of the U.S. On June 8, 2009, the U.S. 6th Circuit Court of Appeals granted EPA a 2-year stay of the mandate in National Cotton Council et al. v. EPA. Before the ruling takes effect on April 9, 2011, EPA plans to issue a final general National Pollutant Discharge Elimination System (NPDES) permit for covered pesticide applications, to assist authorized states to develop their NPDES permits and to provide outreach and education to the regulated community. EPA estimates that the ruling affects approximately 365,000 pesticide applicators that perform 5.6 million pesticide applications annually. EPA’s latest thinking on a number of issues is presented here, including who needs permit coverage for what kinds of pesticide applications, permit limits and conditions, and monitoring and reporting requirements.
Panel Discussion – Regulatory and Policy Issues around Non-Target Mortality and Environmental Fate of Rodenticides
One of the goals of this Symposium was to bring together agricultural and conservation users of rodenticides to discuss the impacts of rodenticides on the environment, examine the current regulatory climate governing their use, and identify ways that users can reduce or eliminate these impacts. Some of the presentations in today’s symposium highlighted specific impacts, and the preceding talk described the scenario of what can happen if an issue related to pesticide impacts ends up in the courts. The three agencies that were represented on this panel (USDA, USFWS, and EPA) have regulatory oversight and enforcement authority for the use of rodenticides and/or the adverse effects resulting from the use of rodenticides. In addition, USDA and FWS are the primary federal users of rodenticides for agriculture and conservation. USDA holds the registrations for a number of rodenticide products for agricultural and conservation purposes. Panelists were asked to describe how Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), Migratory Bird Treaty Act (MBTA), Endangered Species Act (ESA), National Environmental Policy Act (NEPA), the Animal Damage Control Act, and the administration of USDA’s pesticide labels apply to rodenticide adverse effects. Panelists were then asked to bring up an issue within the scope of their agency that they view as problematic for conducting eradication projects. Panelists were also asked to suggest proactive measures that the rodent eradication community can undertake to improve future rodent eradication efforts. Finally, the floor was opened to audience members for questions and comments.
Factors Contributing to the Outbreak of Richardson’s Ground Squirrel Populations in the Canadian Prairies
In the last decade, Richardson’s ground squirrel populations have reached epidemic levels in western Canada. A review of socio-economic conditions and field research findings suggests that such outbreaks are the result of many factors working synergistically on ground squirrel population dynamics and dispersal: 1) drought conditions, 2) poor grassland management, 3) low cattle prices due to bovine spongiform encephalopathy, 4) inefficient rodenticides, 5) loss of predators, and 6) loss of family-size operations to large-scale landowners. In the light of recent outbreaks experienced in western Canada, we now know that the control of Richardson’s ground squirrel populations requires a long-term management program, integrating sustainable grassland management techniques with an effective conservation of mammalian and avian predators, and the sensible use of effective rodenticides. The success of such a multi-faceted management program will depend on the establishment of an effective education program, the institution of incentive programs for a better management of grassland ecosystems, the implementation and enforcement of rules to better monitor the production and distribution of effective poisons, and minimizing excessive use by producers.
Following the escape of 8 Gambian giant pouched rats (Gambian rats) from an exotic pet breeder in 1999, Gambian rats became an established invasive species that persists in the wild on Grassy Key, Florida. Because of their large body size, the free-ranging Gambian rats pose a serious threat to native species and agricultural crops, especially if they find their way into mainland Florida. Initiated in 2005, the USDA Wildlife Services has been conducting an eradication and detection program in the Florida Keys. Today however, detecting, baiting, trapping, and removing the now sparse population of Gambian rats are proving difficult. Therefore, we conducted a laboratory trial with wild-captured Gambian rats from Grassy Kay to test 15 potential materials that could be used for attracting the remaining free-ranging population. We found that a conspecific scent (i.e., feces and urine) from other Gambian rats was the most attractive, but also peanut butter, anise, ginger, and fatty acid scent seemed to attract Gambian rats. In an additional study, we tested the efficacy of 6 commercially available rodenticide baits (all with different formulations of active ingredients) in multiple-choice food trials. We found that brodifacoum (second-generation anticoagulant) and zinc phosphide (acute rodenticide) formulated baits were highly effective. Using these various attractants and rodenticides could be useful for eliminating the sparse population of invading Gambian rats in the Florida Keys.
Voles (Microtus spp. and Arvicola spp.) are the most abundant rodent species in open European landscapes. Due to their preference for agricultural habitats and their enormous reproductive potential, they are often regarded as pests. Several attempts have been made to reduce vole densities using rodenticide baits, gasses, or traps. No matter what method is used, they all bear the problem of voles reinvading from adjacent habitats. We tested a combination of fence and a new kind of trap that enabled terrestrial vole predators to take the captured prey. The combination of fence and traps was tested in a field trial and compared with mesh wire fences and an obstacle-free control line. This three-line setup was installed at each of three locations in Switzerland. Movement patterns of terrestrial predators were recorded by video observation during a 2-year period. Within this period, we made 1,224 observations of mammals; about ¾ of them, 951, were terrestrial predators and 157 were others like hares or hedgehogs. Due to their smaller size, only 116 voles were observed during the same time. Fences with traps were clearly preferred by predators, and their activity was significantly higher along fences with traps, as compared to the two other types. Predators seemed to check traps actively as they moved significantly more often close and parallel to fences with traps. Voles were not only removed from the traps but also caught while moving in the vicinity of the fences. The observed vole movements were ended by a predator in 11% of all instances. We found that barriers with additional trapping devices attracted predators, which started to patrol these fences regularly. Such a physical barrier in combination with its natural guard is a suitable device to protect high-value crops like orchards. As an integrated tool, it will reduce efforts, costs, and environmental impacts of vole control measures. Subsequent to this study, a new Hshaped double wall fence was constructed. This new type gives additional benefits, as it is easier to maintain and allows both terrestrial and avian predators to take captured voles.
At least 137 species of common bamboos of India and rest of Asia seed synchronously at long and supra-annual intervals. These include species belonging to the genera Phyllostachys, Arundinaria, Bambusa, Dendrocalamus, Gigantochloapus, Malocanna, Guadua, Nechouzeaua, Ochlandra, and Thyrostachys. The enormous quantity of seeds shed by these bamboos affect the population dynamics of several vertebrates, including mostly birds, rodents, and wild pigs. The rodents, as generalist seed predators, exhibit a very complex response to the sudden spurt in the availability of nutritious bamboo seeds. In North-east India, the popular saying and belief “when bamboo flowers, famine follows” refers to the phenomenon of gregarious bamboo flowering, massive seed fall, and irruptions in rodent populations, which, after exhausting the bamboo seeds, invade and devour the entire crop fields and stored foods, leading to famine. Such events have been occurring approximately every 40 - 45 years since 1880, the latest being 2005 - 2007 sans any famine. Although 14 species of rodents occur in North-east India, until now there is no strong evidence to identify the species exhibiting population outbreaks. The species suspected to irrupt are Rattus rattus, R. r. brunneusculus, R. bowersi, R. niviventer, and Canomys badius. Similar irruptions of rodent populations in South America has been documented since 1800. These eruptions, termed ratadas, were seen in Oligoryzomys longicaudatus and Abothrix longipilis consequent to flowering of Chusquea quilla. Comparable density increases are seen consequent to masting in trees other than bamboo. Although the mechanism of seed masting is attributed to several hypotheses, predation satiation is the most accepted theory. In this paper, rodent response to masting is discussed in relation to this theory. The non-occurrence of famine in North-east India consequent to 2005-2007 bamboo flowering is mainly due to the effective strategies formulated by the government of India to prevent population buildup of rodents. This seems to be a fine instance of prophylactic approach to rodent management in large areas encompassing several states.
The use of lasers to prevent oiling of waterbirds at a spill is a new concept. Little is known about how some species that could occur at a spill would respond. The objectives of this study were to: 1) identify species that respond to the laser, 2) document the immediate response of waterbirds to the laser, 3) determine if laser treatment during the early evening reduces bird numbers over the course of a night, and 4) determine if the laser treatment has any lasting effect over the short term after treatment has ended. The study was conducted in 2 parts. In Part 1, we used 5 locations in the Sacramento Valley of California. We visited the sites at dusk from October 2007 - March 2008 and opportunistically used the laser on any birds encountered. At each test session, we recorded ambient light levels and the species and number of birds. We fired the laser, then recorded the immediacy and type of responses and the number of birds remaining. A response was considered favorable if the bird left the site. For Part 2, we used a 20-ha marsh in Woodland, Yolo County, California. The study, conducted in March 2008, was divided into 3 periods (pretreatment, treatment, and post-treatment) of 5 days each. We counted birds in the morning and at dusk each day. During the treatment period, we counted the birds at dusk, fired the laser, and then counted any remaining birds. We recorded the same information as described above for the random tests. In part 1, we tested the laser on 18 evenings and fired the laser 129 times at 2,000 birds consisting of 25 species. Overall, 1,212 (61%) birds responded favorably. High proportions of pelicans and cormorants (100%), herons and egrets (99%), geese (93%), and diving ducks (85%) responded favorably. No grebes, coots, shorebirds, gulls responded favorably. Only 10% of the dabbling ducks responded favorably to treatment. In Part 2, we fired the laser 74 times at 3,036 birds consisting of 16 species. Overall, 2,251 (74%) birds responded favorably. High proportions of herons (98%) and dabbling ducks (93%) responded favorably, but only 46% of the diving ducks responded favorably. No coots responded favorably. There was a significant decrease in bird numbers immediately after laser treatment. Bird numbers recorded the next morning were not significantly different from the levels present just before the laser treatment the evening before. There was a significant decrease of 47% in the average number of birds on the treated area from the pretreatment period (x-bar = 873.7; SD = 151.8) to the treatment period (x-bar = 463.9, SD = 171.3). Thereafter, the number of birds during the 5-day post-treatment period (x-bar = 530.8, SD = 206.6) was not significantly different from that during the treatment period. Suggestions are provided on using the laser at a spill event.
The population of ring-billed gulls in the upper Midwest has increased exponentially in recent decades leading to a variety of conflicts including property damage, negative economic impacts, threats to human safety, and potential threats to human health. Some studies have suggested a link between gull fecal droppings and elevated Escherichia coli levels, which result in swim advisories and bans on public beaches. The objectives of the Chicago ring-billed gull damage management project were to reduce the local production of ring-billed gulls, to evaluate the affects limiting gull production has on gull use of beaches, and to reduce the severity of conflicts with gulls including the issuance of swim advisories and swim bans. Between 2007 and 2009, we applied corn oil to 52 - 80% of nests in 2 large gull colonies in Chicago and successfully reduced hatching success and subsequent fledging of 18,000 - 42,000 gulls per year without causing colony abandonment. Fewer hatch year gulls were observed in 2009 on Chicago’s beaches compared to 2007. The reduction in the number of gulls using Chicago beaches has contributed to a reduction in conflicts with gulls, including a decrease in the frequency of swim advisories/bans on Chicago’s beaches in comparison to 2006.
Canada geese are causing a growing concern regarding their impact on public health and safety risks. In Pennsylvania, USDA Wildlife Services manages geese in problematic areas. The purpose of goose management is to reduce damage to agricultural, urban, and natural resources, as well as reducing threats to public health. For this study, three impoundments were monitored bi-weekly from May to September along with a single sampling date in both October and November 2009. Two of the impoundments were managed by the USDA, while the third was an unmanaged control site. The objective of the study was to compare water chemistry and fecal coliform counts from the three sites. Dissolved oxygen, pH, and water temperature were measured, along with fecal and total coliforms, to monitor water quality from the nesting to migration seasons. Results from fecal coliform testing show strong evidence for the benefits of management, with coliform levels up to 3 times higher in the unmanaged impoundment. Based on these findings, we conclude that USDA’s methods of management are effective in reducing health threats as well as improving water quality.
We radio tagged and tracked 50 European starlings between December 2008 and January 2009 at 3 feedlots in the northern Texas Panhandle. Daily fidelity to sites of capture (home feedlots) was different among the 3 radio-tagged cohorts. Cohorts from Sites A and C were recorded at home feedlots on 48 and 59% of tracking days, respectively. The Site B cohort was at its home feedlot 95% of days. There were qualitative differences in use of home feedlots between cohorts A and C. The former were nearly obligate in their use of concentrated animal feeding operations (CAFO), whereas the latter tended to balance their use between CAFO and a nearby urban center. Six birds (12%) used either one or both of the counterpart home feedlots. Of these, 5 permanently switched from their home feedlots and used counterpart home feedlots; one bird captured at Site B alternated between Sites A and C after abandoning its home feedlot. Use of roost sites depended on habitat composition surrounding the study feedlots. Urban habitats were used as roosts by several birds from Sites A and C, whereas birds using Site B roosted at a petroleum refinery and a reservoir. Some Site B individuals used both roost sites during the study period; however, the reservoir was the preferred roost site. Daily activities in habitats away from the home feedlot generally occurred ≤5 km from the home feedlot. For birds from Sites A and C, offsite habitats were mainly urban areas and small CAFO. Increased habitat heterogeneity, as exemplified in our study by urban habitats and CAFO near Sites A and C, seemed to reduce rates of daily use of home feedlots. Heterogeneous environments can complicate management strategies that use DRC-1339 Concentrate for reducing starling numbers at infested CAFO. First, starlings may be erratic in their daily use of a CAFO in complex environments. Secondly, urban areas, when present, may be used as refuges by poisoned birds, leading to adverse public exposure.
Eradication of Invasive House Crow (Corvus splendens) from Socotra Island, Republic of Yemen – Lessons Learned from 15 Years of Facing a Bird Invasion
The house crow is one of the most invasive bird species in the world, affecting more than 25 nations around the Indian Ocean, Arabian Peninsula, and Southeast Asia. It causes problems for development, public hygiene, biodiversity, tourism, and traffic. House crows arrived in 1995 on Socotra Island, Yemen Republic, coming from mainland Yemen by ship. Socotra Island is a UNESCO World Heritage Site, having a unique ecosystem with a larger number of endemic species. Ongoing management did not achieve eradication of the species for more than a decade; however, it kept numbers of the breeding population low. The last 13 birds were finally eradicated in April 2009, thanks to techniques and experienced personnel from abroad and support by the Small Grant Programme of the Global Environmental Facility. More vigilance in dealing with this species, as well as a better transfer of international knowledge to local managers, are required to tackle problems caused by invasive house crows in the affected regions.
More than 300 migratory bird species in Oregon have the potential to nest in highway rights-of-way or on bridges. Because these species are protected under the Migratory Bird Treaty Act (MBTA) and there are no incidental take permits, Oregon Department of Transportation (ODOT) projects may be impeded by nesting birds. In 2006, ODOT contacted USDA Wildlife Services to assist with MBTA compliance. This paper describes the unique nature of the inter-governmental agreement and the success it has brought both agencies.
Predation effects have been studied since the early days of wildlife management, with the goal of wildlife managers to balance wildlife populations with available habitat and management objectives. Still, research and public debate focuses on the degree to which vegetative carrying capacity (K) affects prey and the degree to which predation management could benefit prey species. K, to this point, has not generally considered the secondary effects that predators have on prey habitat availability. When setting wildlife management objectives, the relationship of predation impacts (i.e., factors that may cause mortality in a given species) to prey and available habitat and habitat availability must be examined carefully and understood. This paper discusses classic predator-prey relationships and the potential effects of secondary predation on prey. Managers must consider these effects and relationships to determine if, when, and how to implement an effective wildlife enhancement or predation management strategy.
Influence of Meso-Mammal Predator Control on Predator Landscape-Level Spatial Occupancy in Northern Florida and Southern Georgia, USA
Predator control to enhance avian reproductive success is a controversial issue in wildlife management, yet rarely is the effectiveness of this tool evaluated with respect to the impact it has on predator populations. Understanding predator demographic responses to intense predator reduction efforts has important applied implications, and provides data to answer to public scrutiny. Medium-sized, generalist mammals (i.e., meso-mammalian) are important nest predators of the declining gamebird, the northern bobwhite, and may limit bobwhite populations. To evaluate the effectiveness of intensive predator control on influencing meso-mammal populations, we monitored 4 primary meso-mammal nest predators of bobwhites. These species include raccoon, Virginia opossum, nine-banded armadillo, and bobcat. We used scent stations to monitor predators on 4 study sites (1,300-1,400 ha each) in northern Florida and southern Georgia during 2000-2006. Baseline data were collected in 2000 for all study sites. During 2001-2003, 2 sites received intensive meso-mammal predator reduction during the 7-month bobwhite breeding season, whereas the other two sites served as controls with no reduction occurring. After 3 years, the treatments were reversed. Using predator detection at scent stations, we modeled the probability that predators used 25-ha patches across the study sites via a community occupancy model. We examined the probability of patch use between years to determine the effectiveness of predator reduction and the resilience of predator populations to management. We removed a total of 5,161 meso-mammals from our study areas. Our results show meso-mammal predator control, as done on our study area, was sufficiently intensive enough to reduce predator use across target sites, but continued reduction would be needed to reduce predator patch use between years. Our findings demonstrate that a predator community can be reduced at the local scale; however, the predators remain on the greater landscape thereby minimizing potential for negative impacts on ecosystem integrity.
Black bear populations are increasing throughout North America. When areas of black bear population expansion overlap regions of substantial human use, conflict can ensue. Human-bear conflicts can have negative economic, health/safety, and social impacts. Attraction to human foods brings bears into more frequent contact with people, resulting in a higher probability of negative human-bear encounters. In order to achieve successful management of human-bear conflicts, the use of bear-resistant lids outfitted on dumpsters is one management tool. We evaluated the efficacy of Interagency Grizzly Bear Committee-approved, modified, bear-resistant lids that were installed on dumpsters in a community in northwestern New Jersey. Black bear sows exhibiting nuisance behavior were trapped in the community at dumpster sites, outfitted with either VHF or GPS satellite collars, and their movements were tracked for the year prior to the installation of the retrofitted bear-resistant dumpster lids. After the lids were installed, movement patterns of the sows were monitored to determine if bears altered their behavior and left the area when dumpster access was no longer available. Residents of the community were also surveyed and offered educational programs regarding the black bear population in their community.
From the perspective of a private wildlife control operator, I share experiences and advice in dealing with problem urban coyotes, including strategies to deal with municipalities, the public, and the media. New technologies, such as geographic mapping programs, help identify habitats where problem coyotes are likely sheltering during daytime, and where capture equipment can be installed. Remote cameras are invaluable in surveillance of potential trap sites for non-target animals, and in monitoring traps sets so captured animals can be removed quickly. Necropsies should be done to evaluate the health of problem coyotes taken. Intentional feeding may cause coyotes to become aggressive toward pets and people, even in autumn when coyotes are typically less territorial. I discuss why I do not typically encourage residents to conduct hazing on urban coyotes, and why relocation of problem coyotes is not advisable and is often illegal. Professionals who conduct urban coyote control have an opportunity to help educate the public about scientifically-based wildlife management, and how to deal with problem coyotes. Web sites, news releases, and public service announcements can all be useful educational tools.
The Colorado Division of Wildlife (CDOW) recently conducted an urban coyote symposium for city decisionmakers in the Denver metro area in response to a burgeoning coyote problem, including multiple attacks on humans. The symposium was well organized, but it conveyed typical messages about managing human-coyote conflicts that I contend are misconceptions and misinformation. They include: we’re encroaching on coyote habitat; coyotes that attack pets and people are abnormal; lethal control should only be used as a last resort; killing coyotes simply produces more coyotes; we should coexist with our “coyote neighbors”; hazing is the answer; and “it’s a people problem, not a coyote problem”. I dispute these concepts, and I contend that promoting the components of coexistence can actually foster human-coyote conflicts. In the process I also support the case for lethal control.
Importance of Early Experience with Flavor on Subsequent Food Preferences by Young Coyotes (Canis latrans)
Coyote food habits are well documented, but little is known about the mechanisms driving food selection. Early experience with flavors has been documented to be important in the foraging decisions made by such species as cattle, goats, rats, mice, and domestic dogs. We examined the effect of early experience with flavors on the subsequent food preferences of young coyotes. Part 1 of the study examined the effects of flavors presented in milk, while Part 2 examined the effects of flavors presented in solid food. In both parts, coyote pups were exposed to the treatments and subsequently tested with a series of two-choice tests. Results of the study indicate that early experience with flavor is not the sole mechanism driving food selection in young coyotes. These data support the hypothesis that young coyotes feed opportunistically.
When livestock are killed by predators, circumstantial evidence is often the only information available to determine which predator species made the kill. Evidence can consist of rake marks, scat, hair, attack points, tracks, sightings, and canine punctures. Canine punctures in particular can be informative because they offer the most direct evidence of attack, particularly if they are linked to tissue hemorrhaging. When investigating canine punctures, a common technique to identify the predator species is to measure the canine cusp spread for maxillary and mandibular tips as measured from the maxillary to maxillary tip or mandibular to mandibular tip. The assumption is that different predator species will have different and distinct canine spread. Surprisingly, little has been published on canine spread and comparing different carnivore species, leaving wildlife managers unable to reliably use this technique for predator identification. During 2008, we started a project to assess the width of canine spread in carnivores. The majority of information gathered to date shows a narrow range of measurements for coyotes and broad variation in feral/free ranging dogs that can overlap coyote measurements. The information provided on scientifically measured canine spread will assist the wildlife damage manager in determining the actual predatory species, especially when used with additional evidence gathered on site.
Modeling the Economic Impact of Feral Swine-Transmitted Foot-and-Mouth Disease: A Case Study from Missouri
Invasive feral swine combine a number of characteristics (e.g., high mobility, high fecundity, destructive behavior, reservoir of diseases, etc.) that make them one of the most serious wildlife threats to American agriculture. Additionally, feral swine are susceptible to foot-and-mouth disease (FMD) infection and could play a significant role in spreading and maintaining FMD if it was introduced to the U.S. Outbreaks of FMD also have devastating economic impacts and cause the loss of billions of dollars to the agricultural economy. Problems associated with spread and control would be exacerbated if FMD was contracted and spread by feral swine, threatening the 4.3 million head of cattle and 3.1 million head of domestic hogs in Missouri. This study uses a bioeconomic modeling framework to estimate the direct and indirect economic impacts of FMD being transmitted from feral swine to Missouri’s livestock. It is predicted that if FMD occurred in feral swine in Missouri, the disease outbreak would last 45 days, resulting in 18,658 head of livestock being destroyed, and would cost the state a minimum of $7.5 million.
Bovine tuberculosis (bTB) is a contagious disease capable of infecting wildlife, livestock, and humans. While once common in U.S. livestock, the disease has historically been rare in wildlife. However, in Michigan’s Northeastern Lower Peninsula (NELP), bTB is endemic in white-tailed deer, and evidence suggests transmission to cattle. The disease has also been documented in other wildlife species including raccoons, which frequent areas used by domestic cattle. Such interactions could facilitate transmission of bTB, but whether free-ranging raccoons shed the causative agent, Mycobacterium bovis, is unknown. We trapped raccoons on private and public land in 5 counties in the NELP from which we collected tissue samples, oral/nasal swabs, and fecal samples to determine if raccoons shed M. bovis. Culture results from 2 of 144 usable tissue sample submissions were positive for bTB, suggesting an apparent local prevalence of 1.4%, a decrease from previous estimates. Using currently available culturing techniques, swabs and feces from one tissue culture-positive animal were negative for M. bovis. While this small sample size of positive animals makes definitive conclusions difficult, we believe that although raccoons may serve as a reservoir or a spillover host for bTB, transmission risk to cattle is minimal. Further research into this arena, as well as continued refinement of culturing techniques to detect low levels of M. bovis, is warranted.
Bovine tuberculosis is endemic in white-tailed deer in Michigan’s Northeastern Lower Peninsula (NELP), and evidence suggests transmission to domestic cattle. One source of transmission is through feed shared between deer and cattle as a result of deer access to stored cattle feed. Fences (2-3 m in height) have been erected to surround stored feed on at least 50 cattle farms in the NELP in order to prevent deer access. However, gate closure by landowners remains a problem. We investigated the use of polyvinyl chloride (PVC) curtains installed at gate openings as a tool to deter deer from entering stored feed areas. Deer activity was monitored through the use of infrared digital cameras and by recording deer tracks inside and outside stored feed facilities. Two treatment and two control sites were established. On the first treatment site, deer tracks inside the fenced feed area decreased post-treatment from 9 to 0. Tracks within 5 m outside the fence decreased from 28 to 13. Photographs of deer entering or exiting the gate decreased from 23 to 0. Photographs of deer near stored hay decreased from 2 to 0. No deer activity was observed on either control site or the second treatment site during the study period. While sample sizes are too small for statistical analysis, we believe the use of PVC curtains to deter deer from stored feed areas has merit and deserves additional intensive research.
In 2004, raccoon variant rabies moved westward from Pennsylvania into Ohio. In an effort to prevent further spread across Ohio, USDA Wildlife Services expanded the Oral Rabies Vaccination (ORV) boundary west toward Cleveland. To assist the Wildlife Services ORV Program to better understand how rabies might move through an urban area, and to help develop the best vaccination strategy to stop its spread, researchers at the USDA National Wildlife Research Center initiated a series of studies. As part of these studies, we deployed 10 remote download GPS collars on raccoons in urban areas of Cleveland. Remote download GPS collars offer advantages and disadvantages over traditional VHF telemetry and conventional “store on board” GPS collars, particularly in urban environments. Raccoons may inhabit culverts or sewer pipes that are inaccessible to humans. As a result, collars programmed to drop off may be lost and the data never recovered. Remote download capability allows researchers to retrieve data without collecting the collar. However, remote download collars tend to be larger and bulkier than other models. Out of 10 collars deployed, 1 went missing within a day of deployment, a second stopped transmitting after 5 months, and one raccoon died (this collar was recovered and later re-deployed). Data collection of nightly locations from 8 collars is ongoing. Locations are downloaded every 5 weeks. Data collected to date suggests raccoons are restricting their space use to small green-spaces when available, but also may inhabit abandoned houses. We believe this research represents the first use of remote download GPS collars on raccoons.
A rabies epizootic occurred in striped skunks from 1988-1993 in a previously rabies-free area of northwestern Wyoming. USDA APHIS Wildlife Services (WS) cooperated with state and local officials by providing a rabies monitoring and depopulation program starting in 1990. Wyoming WS asked for assistance in 1991 from the National Wildlife Research Center (NWRC) to analyze the epizootic’s movements. The goal was to address the public’s concerns about their health and safety and that of their domestic animals and livestock. All rabid skunks were diagnosed by the Wyoming State Veterinary Laboratory (WSVL) using standardized fluorescent antibody testing of brain tissues. The “Index Case” was collected on August 15, 1988 near Cowley. The epizootic moved radially out from this location and was limited by skunk habitat that was itself constrained by physiographic barriers. Rabies spread up and down Polecat and Sage Creeks before entering the rest of the lower Shoshone River Basin (SRB). It then moved both downstream to the Bighorn Lake and upstream toward Yellowstone National Park. However, when this epizootic ended in 1993, it had reached only the lower SRB downstream from Buffalo Bill’s Reservoir and Canyon. This area has been rabies-free ever since. Over the years various analytical techniques have been utilized by the authors to better understand and describe this epizootic. These have included: traditional county surveillance data (1988); GPS, digitized, and geocoded locations (1991); and GIS databases with and rudimentary landscape epidemiology (1992). Following the epizootic, we used more detailed GIS databases as they were developed for land cover (i.e., habitat), hydrology, and human populations from 1999 - 2006. Subsequent rabies analyses have included: movement of the monthly mean locations (2007); spatial ellipsoid movements indicating “wave fronts” or “crests” (2008); and multivariate movement maps (MMM) (2009). MMM were used to illustrate the rabies front(s) with the instantaneous and spatially described density of cases and directional flow of spreading disease. The advantages and drawbacks of each analysis tool are discussed. The evolution of these different analytical tools and their uses should assist epidemiologists in analyzing and understanding future rabies epizootics.
Effect of a Feed-Through Insecticide (Imidacloprid) on the Flea Index of a Norway Rat (Rattus norvegicus) Focus in Los Angeles, California
Norway rats and their fleas are associated with transmitting diseases, such as murine typhus and plague, to humans. The use of rodenticide baits may increase human exposure to rodent fleas due to loss of their preferred host. Therefore, flea control is an important component of risk reduction. However, the use of insecticide powder or spray can be difficult in certain situations. In this field study we used a feed-through insecticide, imidacloprid, in a grain-based pellet formulation without a rodenticide to determine the effect on the flea index of a well defined, problematic Norway rat focus in a dense urban area of Los Angeles. The flea index was determined to be 12.9 (116 fleas/9 rats) 5 days prior to applying the product. Rats were allowed to feed on the pellets ad libitum for 48 hours, in the presence of previously existing competing food sources. Flea counts were then taken, and again 7 days later, resulting in flea indices of 2.3 (25/11) and 1.5 (23/15), respectively. Since this field trial was conducted in a very dynamic urban area, attempts to survey a concurrent control group were not successful. However, Norway rat surveys conducted in the previous 4 years from the same urban area for the same months, July and August, produced flea indices of 7.4 and 10.1, respectively. In this field trial, we found that a rodent bait formulation containing imidacloprid reduced the flea index of a Norway rat focus from 12.9 to 2.3 (82%) in 48 hours, and to 1.5 (88%) 7 days later.
Papers presented at two long-running conferences, the Australasian Vertebrate Pest Conference and the USA Vertebrate Pest Conference, were reviewed to examine changes in the field of vertebrate pest management over the last few decades. At both conferences, there has been a shift in focus from pest impacts on production (crop, livestock, forestry etc.) to impacts on conservation values. Papers have also become more focussed with a decrease in papers on pest problem overviews. There were surprisingly few papers focussing on the human dimensions of vertebrate pest management, despite general acknowledgment that the public have become more involved in pest management decision-making. The number of papers presented and number of pest species addressed has also increased, indicating the importance of these conferences to pest management professionals for sharing information and ideas.
New Zealand has many invasive vertebrate species that adversely affect native biota, compete with livestock, and spread diseases. Large-scale management of the most critical pests is achieved mainly by lethal control. This includes aerial application of the controversial toxin sodium fluoroacetate (1080), despite vociferous opposition from those concerned about potential non-target deaths, environmental contamination, and animal welfare impacts. We have borrowed a framework from animal welfare science, namely the ‘3Rs’ (reduction, refinement, and replacement), to address some of the concerns about the use of aerial poisoning while sustaining its cost-efficiency. The first aim was to reduce the amount of toxin used so that undesirable nontarget impacts are minimised. A range of projects have: 1) developed a method to identify the high-risk habitat within a landscape that needs to be targeted and, equally importantly, the low-risk habitat over which toxic bait does not need to be sown; and 2) optimised the combinations of prefeeding, sowing rate, and bait distribution to achieve the desired percentage kills at the lowest cost and lowest sowing rate of poison bait. To address the second aim, refining toxin use, we have improved target specificity by developing repellents to minimise unintended bykill of non-target species such as deer, and by identifying long-term strategies that minimise the total number of animals killed. The final aim, replacement of 1080, focuses on the search for alternatives, such as fertility control. It also involves development of complementary tools, such as tuberculosis vaccines, that may reduce the frequency or need for repeated use of 1080. This integrated ‘3Rs’ approach has quickly led to changes to operational practice by management agencies, with some operations now using up to 92% less toxic bait than usual, and other operations switching from aerial 1080 poisoning to ground-based non-1080 approaches for ongoing control. Looking forward, the ‘3Rs’ approach offers a framework for continuous improvement in the use of control tools for a wide range of species, whilst also providing a clear pathway to complementary or alternative approaches.
The brushtail possum, introduced to New Zealand in 1858, is a significant conservation pest and a major vector of bovine tuberculosis. Previous control-simulation studies have suggested that aerial delivery of bait containing sodium fluoroacetate (1080) is the most cost effective (large scale) possum control strategy. Over the past decade, considerable improvements in groundcontrol techniques have been developed by private contractors and bait manufacturers. These techniques are not reliant on 1080, and there have been major cost reductions as the new baits and delivery mechanisms have been optimized. In addition to this, our research team (in collaboration with Connovation Research Ltd.) have recently developed a new bait station design that has the potential to be left out in the field for up to 5 years without the need for servicing. These devices are self setting and have the ability to deliver gel or liquid spray, and ‘target-specific’ toxicants. Preliminary cost analysis suggests that this new bait station design has the potential to save NZ$21 million per annum from the amount currently spent on possum ground control.
Vertebrate Pest Control Research Advisory Committee (VPCRAC): California’s Approach to Supporting Vertebrate Pest Control
As a result of increasing concern over rodenticide registration, in 1990, the California Legislature passed a law to collect $0.50 per pound surcharge on all vertebrate pest control materials sold by county agricultural commissioners in the state of California. Monies collected are used to fund research required to maintain the state’s current vertebrate pesticide registrations, to improve existing rodenticides, and to find new materials and methods to solve California’s vertebrate pest problems. A Vertebrate Pest Control Research Advisory Committee was established to administer this fund and set research priorities. To date, the program has raised more than $9 million to meet its objectives. The history, operation, and accomplishments of the surcharge fund are discussed in this report. A summary of projects funded is presented.
This project was undertaken to provide a flexible multimedia education and outreach program on vertebrate pest control in agricultural settings. The target audience for this concept is the California agricultural industry and urban members of the public who are dealing with California ground squirrel, pocket gopher, and meadow vole problems. Online users are able to access various learning tools for all three species. Each program consists of an interactive training course, video learning, study guide, two section quizzes, and a final exam with an option to obtain 2-hours of California Department of Pesticide Regulation (DPR) or Structural Pest Control Board (SPCB) continuing education credit. The site also has a Facts and Questions section, podcasts of the training programs, and links to a YouTube, Facebook, and Twitter pages. The training programs are available to DPR certified pesticide applicators, SPCB licensed applicators and the general public. All educational content is capable of being added to or amended from any location, via the Internet. In addition to educating users, the website seamlessly collects statistical data and voluntary information from users (i.e., email messages and website comments). The success and wide availability of internet-based training programs demonstrate the site’s potential for use in statewide continuing education and in pesticide applicator certification efforts related to vertebrate pest control.
The concepts and practices of Integrated Pest Management (IPM) are historically grounded in programs aimed at insects and disease-causing organisms affecting agriculture. When applied to vertebrates, IPM concepts have most often been used in rodent control programs. Still, IPM is a powerful model that arguably can, and should, apply to conflicts with any “pest” or problem-causing organism. It may be time to examine contemporary IPM approaches and their relation to traditional vertebrate pest control more closely. Vertebrate IPM should encompass not only the development of sound and practical steps to shape decision-making and actions, but a dialogue about ethics as well. From such dialogue, codes of practice that combine IPM concepts with standards developed elsewhere for vertebrate pest control should be forthcoming.
This study was undertaken to demonstrate and assess the efficacy of a new outreach education tool, an interactive touch-screen computer (kiosk) for ground squirrel control education. The target audience for the concept is the California agricultural industry and urban members of the public who are dealing with ground squirrel problems. Users of the computer kiosk are able to access various learning tools: a learning library, a quiz, video learning, an interactive decision-making tool, and they are able to print information and certificates. The computer kiosks are available at select California County Agricultural Commissioner offices. They are networked (computer linked) so that the education content is capable of being added to or amended from remote locations. In addition, the kiosks seamlessly gather statistical data and also collect voluntary information from users (i.e. email addresses and comments). The success of the computer kiosks demonstrated their potential for use in statewide continuing education and pesticide applicator certification efforts related to vertebrate pest control.
Some ready-to-use rodenticide baits against synanthrophic mice and rats exhibit an intense scent of vanilla, chocolate, peanut, or hazelnut. The effects of these additives on bait palatability are unclear. The aim of this study was to test whether flavoured food is more attractive to naïve rodents than natural (untreated) food. The attractiveness of flavoured against natural oat flakes was tested on wild strain groups of rodents. We tested vanilla, chocolate, hazelnut, and peanut flavour. House mice (group size 13 to 23 mice), roof rats (group size 5 to 8 rats) and brown rats (group size 5 to 7 rats) were introduced to test chambers (rats: 6.2 m², mice: 5 m²) for choice experiments. Flavoured and natural food as well as water was offered ad libitum for 12 days. Each day, the amount of consumed food was determined by weighting the remaining food, and food and water were replenished. All flavours that were tested on house mice had a positive effect on bait uptake, and the mice took up more flavoured than untreated food (hazelnut 57.7%, chocolate 61.2%, peanut 62%, and vanilla 73.1% of total food uptake). The effect on food uptake was not significantly different between flavours. Roof rats were repelled by chocolate and hazelnut (7.2% and 30.4% of total food uptake, respectively), whereas vanilla flavour had no clear effect on food consumption (51.6% of total food uptake). Similar effects were observed for bait consumption of brown rats, where chocolate flavour had a negative effect on food uptake (28.2% of total food uptake) and hazelnut flavour was neutral in terms of bait attractivity (50.0% of total food uptake). We conclude that the addition of an artificial flavour may increase the attractiveness of rodent baits to house mice, whereas it can reduce bait uptake in both rat species and has thus a detrimental effect on bait attractiveness. The different reaction of mice and rats to flavoured food is explained by the fact that house mice are neophilic, whereas both rat species avoid new stimuli and are neophobic.
Tranquilizer darts are designed to administer a compound from a distance, utilizing low velocities to minimize unnecessary injury to the animal by excessive penetration of the dart. As a result, effective distances and subsequent accuracy of the dart are problematic. It was hypothesized that a minor modification to commercially-available tranquilizer darts would allow greater velocities to be utilized by reducing some of the impact force. This should increase the effective distance of the darts while reducing potential damage to target animals if higher velocities were utilized. A foam-based conventional earplug was modified by cutting it in half to fit over a tranquilizer dart needle. Velocity and calculated impact energy produced from 2.0-cc practice transmitter darts were recorded for treatment and control darts projected at a distance of 13.72 m at two velocities. Degree of dart penetration into a block comprised of layers of a foam insulation material was recorded. Relative accuracy of darts was also collected. While no differences were observed in dart accuracy, velocity, or projected impact energy (p > 0.05), penetration of darts into the insulation block at the higher test velocity was lower (p < 0.05) for treatment darts (11.82 ± 0.30 cm) compared to controls (13.17 ± 0.36 cm). However, dart penetration into the hip of a euthanatized dog was similar (p > 0.70) between the treatment (2.21 ± 0.77 cm) and controls (2.68 ± 0.96 cm) at the higher velocity. It also appeared that degree of dart penetration was highly influenced by the angle of impact relative to the tissue. Based on dart penetration results in animal tissue, the foam based dart modification was not an effective method to reduce impact force of tranquilizer darts.
Determining if White-Flash and Infrared-Flash Camera Traps Have Different Capture Rates at Bait Stations for the Brushtail Possum, Trichosurus vulpecula
The use of infrared-flash camera traps has increased dramatically over the past ten years particularly for capturerecapture population studies of distinctly-marked species. However, to use capture-recapture with the more inconspicuous species, high-quality colour imaging (and therefore white flash) is required. A potential problem with white flash is that it may negatively affect behaviour, in this case at bait stations, therefore causing results that do not truly represent possum activity. Possums were used in this study to compare two different types of camera trap: infrared and white flash. Camera traps were placed to take images of possums visiting bait stations, and the number of possum visits was used to determine if white-flash cameras gave different results to infrared-flash cameras. The white-flash cameras had slightly higher possum visits than infrared-flash cameras but the difference was not significant (P=0.437). Over time, the number of possum events (P=0.62) and the amount of time possums spent at the stations did not differ significantly (P=0.81). There was also no difference in the amount of bait taken by possums at white flash compared to infrared stations (P=0.61). Results show possums are not likely to be affected by white-flash cameras compared to infrared-flash cameras. This study therefore showed that there is unlikely to be any behavioural disadvantage in using white flash over infrared, allowing white-flash cameras to be investigated for their potential in identifying individual possums, and as a monitoring tool in control operations.
The clearing of land for agriculture and the establishment of forestry plantations in Tasmania has led to changes in the distribution and population density of mammalian wildlife species. Populations of Bennett’s wallaby, Tasmanian pademelon, and common brushtail possum appear to have significantly increased over the past 50 years. Management of these and other species, including Forester kangaroo and introduced fallow deer on private land, is a contentious issue for landowners, animal welfare groups, and the government. Many farmers believe that browsing by native wildlife on pastures is significant and results in a considerable financial impost. However, limited research has been undertaken to quantify this wildlife browsing. The main control methods for these wildlife species include exclusion fencing, shooting, trapping, and poisoning. In 2005, the use of the poison 1080 (sodium monofluoroacetate) to kill wildlife was banned from use on public lands, and the Tasmanian Government plans to cease all use by 2015. This study investigated the effects of browsing wildlife on pasture within this region. We used a split plot design, consisting of 2 main treatments with 9 sub-plot treatments, to determine browse impact. Significant reductions in pasture biomass were recorded. The severity of browsing was affected by distance from native vegetation and also varied seasonally. Browsing damage declined with distance from native vegetation edge and was best explained by a logistic relationship. Browsing damage was severe during winter 2008 and varied between 100% at 25 m and 68% at 800 m from native vegetation edge. Browsing wildlife had the least impact during spring 2009 and reductions varied between 64% at 25 m and 0% at 800 m from native vegetation edge. The availability of pasture was found to be a determining factor in the distance and direction that wildlife would travel to browse. Browsing by wildlife also resulted in a reduction in ground cover.
The objective of establishing protected areas should be made to tally with needs and aspirations of the local community. Interaction between the local populace and the ecosystem plays a significant role in the determination of effective management. Overgrazing by cattle and deforestation by human activities over time has denuded the Obudu Cattle Ranch, Cross River State, Nigeria, of its lush natural flora. Consequently, its productivity as grassland has drastically been reduced. Denudation has exposed the surface soils in a number of places to crustation, creating conditions unfavourable for plant growth and has also led to the domination of the ranch by undesirable plant communities that now pose a big threat to the palatable species. These conditions also affect the wild animal species, such as roan antelopes, to encroach on farmlands and destroy agricultural produce. The free area is under socio-cultural activities. There is much sense in the concept that local people should be allowed to utilize resources from protected areas. Nevertheless, this is hard when the future of so many people is at stake from destructive land and resource uses. The most effective means of reducing the conflict between local people and wildlife is through land-use planning, where activities that are non-attractive to wild animals should be encouraged in areas adjacent to the ranch.