Rats, deer mice, and other vertebrate pests cause billions of dollars' worth of damage to fruit and nut crops every year. Learn to recognize signs of rodent damage and how to protect your trees and your crop.

Rodenticides are often used to control burrowing rodents but have not been overly efficacious for Belding’s ground squirrels due to poor bait acceptance. This has left alfalfa growers searching for alternative options for controlling this rodent species. As such, we tested aluminum phosphide and gas cartridge burrow fumigation in an alfalfa field in Butte Valley, CA, to determine if either of these approaches were efficacious and cost effective for controlling Belding’s ground squirrels. A comparison of the number of burrows treated and the number of burrows reopened 48-hours post-treatment indicated that both burrow fumigants were highly effective (aluminum phosphide = 94-98%, gas cartridges = 100%). The average cost per application was $1.05 and $2.92 for aluminum phosphide and gas cartridges, respectively. Given the almost 3-fold difference in cost of application between the two approaches, aluminum phosphide appears to be the more practical approach for Belding’s ground squirrel control. Although we currently lack an approach for estimating the amount of damage that Belding’s ground squirrels are likely to cause to an alfalfa field, it seems plausible that burrow fumigation could be a cost effective approach to reduce damage caused by this species, particularly if long-term control can be obtained. Possible long-term management options for Belding’s ground squirrels are discussed.

Anticoagulant rodenticides have been detected in many species of wildlife worldwide; yet the origins, exposure pathways, and effects of this exposure are not well understood. Furthermore, to accurately characterize the risks from rodenticide use, information is needed on what proportion of populations are being exposed, what proportion of the exposed individuals are affected, and in what ways. The relationship between anticoagulant rodenticide concentrations found in wildlife and the rate of mortality or illness is the subject of much current research. Residue levels observed in liver and whole body analyses vary, and overlap extensively among apparently healthy asymptomatic individuals and sublethal and lethal cases. Results from laboratory studies also show there can be wide variability in lethal and sublethal effects among and within taxonomic groups. Correlating the sublethal and reproductive effects observed in laboratory studies with realistic exposure scenarios and effects in the wild is needed to improve risk assessments. For species with limited numbers/declining populations, a critical question is whether the rodenticide exposure documented in individual animals inhibit population growth or contribute to population declines by lowering survival and reproductive success. This information is essential to the regulatory agencies that must weigh the risks and benefits of rodenticide uses and identify restrictions that are effective in reducing risks to wildlife. A primary objective of this symposium was to facilitate communication between regulators and researchers. Current research on many of these topics was presented, and was followed by discussions on how to improve our understanding of what factors lead to wildlife exposure and improve our ability to assess the effects of exposure on individuals and populations. A collaborative approach will be developed to design studies that provide regulatory and wildlife management agencies with additional science on which to base their decisions.

Predator issues related to interactions with livestock and poultry represent a state, national, and international issue. Predators are important for healthy ecosystems; however, with increased interactions between predators and agricultural animals there is also an increased likelihood of predator depredation. The 4-H Youth Development Program is a national nonformal youth education program. Annually, over 1.5 million youth participate in 4-H Animal Science projects, mainly agricultural animals. 4-H youth who raise agricultural animals face issues of predator-livestock interactions. A 4-H curriculum was developed to help youth learn about predator-livestock interactions and strategies to mitigate these issues through improved animal husbandry. Pilot research on the use of the curriculum revealed improved knowledge among participating youth, as well as the application of mitigation strategies to youths’ own practice and outreach to their communities through a service-learning project.

In terms of internet access, California farmers are some of the most well-connected in the country. According to the USDA, 70% of farms in the U.S. have access to the web as of 2015. In California, 93% of counties exceed that national average. This prompts us to take advantage of the opportunity to employ passive extension approaches, such as websites, which can save both time and resources for Extension audiences and personnel alike. Because digital media can be distributed without the expenses associated with static print resources, this allows us to update our information platforms with greater ease and frequency. Our goal is not to replace print publications, but to adapt Extension resources for a web context and thus connect with a large and geographically extensive audience, especially those who may not customarily seek or have access to more traditional Extension services. A website allows homeowners, landowners, and pest-control professionals to consult this resource freely, at their leisure, and to adopt best management practices more quickly. However, the movement toward cloud-based resources comes with greater web familiarity and thus greater expectations for the websites people use. We are currently developing a ground squirrel best management practices website. In order to provide a user-oriented experience comparable to that of other digital media resources, we need to consider the specific needs and behaviors of a web-based audience. We aim to achieve this by synthesizing new and existing resources into consumable, approachable content on a website that focuses on usability, clarity, visual impact, and site-wide cohesion. We will discuss these goals and how we achieved them.

A common adage is “you can’t manage what you can’t measure.” How applicable this saying may be to wildlife conservation and management is debatable; however, understanding the “where,” “who,” and “why” of human-wildlife conflict can help managers evaluate and prioritize incident response and conflict mitigation efforts. It is critical to note that no tracking or reporting system is capable of effectively capturing all human-wildlife incidents. The format and functionality of the tracking system, how the system is advertised to the public, and who manages the system are all important factors in the accessibility, utility, and success of each tracking system. Here, we examine three different systems for tracking reported human-coyote incidents and encounters in California: 1) the Wildlife Incident Reporting system, operated by the California Department of Fish and Wildlife; 2) Coyote Cacher, operated by the University of California - Agricultural and Natural Resources Cooperative Extension; and 3) iNaturalist, a citizen science initiative, operated by a non-governmental organization. We find that because each system offers different incentives to the public (and poses different potential challenges or barriers to reporting), each receives a significantly different volume of coyote reports. Each system provides a unique perspective of reported human-coyote conflicts in California. Understanding these differences and being cognizant of the inherent or potential limitations of a reporting system are crucial for integrated, scientifically defensible, and robust wildlife management, effective policy development, and informed decision-making.

Rodenticides are an essential tool in the integrated pest management (IPM) of infestations of commensal rodents. With the introduction of Assembly Bill 2422 California Natural Predator Protection Act, the State of California is potentially facing a future with serious restrictions on the use of anticoagulant rodenticides to manage commensal rodents in urban areas. Assembly Bill 2422 has been proposed to protect predators from rodenticide poisoning and seeks to significantly restrict the application of first and second generation anticoagulant rodenticides for use in many urban and no-urban areas of California. Exclusion and cultural practices, such as landscape management and sanitation, are important and successful tools for managing rodent populations. However, quick and efficient control of commensal rodent infestations often necessitates the use of rodenticides. While rodenticide is an important tool, exposure of wildlife to anticoagulant rodenticides has been evident for many years in the state of California. When rodents are consumed by predators, second generation anticoagulant rodenticides can be detected as residues in the livers of predators. Many species of animals are documented as having succumbed to rodenticide toxicosis, however the effects of chronic, sub-lethal exposure to predators are not well understood. This paper will discuss the current and proposed changes to rodenticide legislation in California, impacts of the legislation on communities across California, and gaps in research preventing the adoption of evidence-based best management strategies for rodent control. In order to improve the success of commensal rodent control programs in California, effective strategies for rodent management must be developed.

In many cities across the United States, incidences of coyote encounters (Canis latrans) and human-coyote conflicts are rising. This is especially true for cities in Southern California, where conflicts including pet attacks have been recorded since the 1960s. The only coyote-related human fatality in the United States occurred in Southern California in 1981 and, although no fatal attacks have occurred since, coyote bites to humans are still occurring. Coyote attacks on pets appear to be common in Southern California; however, data are lacking in this area of human-coyote conflicts. This paper examines data from multiple sources that record human-coyote conflicts in Southern California. Coyote reports have been more frequently received by the entities involved in this analysis as their recording time progresses, with data from 243 cities and unincorporated areas suggesting that the majority of reports (68%) are related to non-conflict events. Conflicts were significantly higher in the pup-rearing season compared to the breeding season. There appears to be spatial clustering of coyote reports from Los Angeles County; however, complex analysis is needed to determine the relationship between frequency of complaints and land use in all of the counties to help determine what is driving human-coyote conflicts in Southern California.

Although coyotes are a natural component of southern California ecosystems, they are sometimes considered a nuisance because their opportunistic habits and tolerance for urban and suburban environments bring them into conflict with people. Recent attacks on people and pets have increasingly led to lethal control of nuisance animals, yet it is unclear whether the demographic distribution of nuisance individuals is representative of the coyote population as a whole. We used two methods, cementum annuli analysis and tooth wear, to estimate the age of coyotes collected as nuisance or road-killed animals in southern California. Age estimates based on tooth wear, a non-lethal method, were broadly similar to those from cementum annuli analysis, although tooth-wear estimates were highly variable and tended to overestimate age, especially for younger individuals. The demographic structure of coyotes collected as nuisance animals was biased toward young adults and males, which suggests that this demographic class may be more likely to killed by control efforts, possibly because their behavior creates greater opportunities for conflict with people.

Secondary exposure to anticoagulant rodenticides (ARs) remains a significant problem for wild carnivores living at the urban-wildland interface. Although direct mortality is the most obvious concern, AR exposure may also cause subtle, sub-lethal effects, such as reduced body condition and increased parasite loads, that ultimately contribute to poorer performance at the population level. However, relatively little is known about such effects on wild animals, or about the environmental factors that contribute to AR exposure. We examined relationships between levels of AR exposure, demographic factors, and landscape variables associated with urbanization, for coyotes (Canis latrans) from urban Los Angeles and Orange counties, California. AR exposure was estimated from residue assays of livers from 353 carcasses, collected opportunistically as road kills or euthanized nuisance animals from 2015 to 2018. We also conducted veterinary necropsies on a subset of 50 carcasses to investigate effects of AR exposure on body weight, overall condition, and parasite burdens. Nearly all coyotes (98%) contained residues of at least one AR, with second-generation ARs (SGARs) detected in 97%, first-generation ARs (FGARs) detected in 75%, and 66% exposed to both types. Individual coyotes had residues of 0-6 compounds (mode = 4), with three SGARs (bromadiolone, brodifacuom, difethialone) and one FGAR (diphacinone) detected often (≥65 coyotes). Adults were exposed to more ARs and had significantly higher residue concentrations than juveniles. Road-killed coyotes were over-represented among coyotes with high numbers of SGARs and had significantly higher SGAR residue levels than euthanized ones. Contrary to our expectations, landscape patterns suggested higher numbers and residue concentrations of SGARs in coyotes associated with less intensive urban development. Very few coyotes (6 of 353) showed any evidence of mange, and these animals had similar AR numbers and residue concentrations to those without mange. Of the 50 animals that we necropsied thoroughly, coyotes with obvious internal hemorrhage tended to have high residue concentrations of SGARs, while those exposed to multiple FGAR compounds and with high FGAR residue concentrations tended to be in poorer body condition. ARs are an important tool for managing rodent pests but given the ubiquitous exposure of coyotes to ARs and evidence of potential sub-lethal effects, notably from FGARs, we need more information on pathways of exposure and better strategies to reduce the total amount of ARs on the landscape.