Rodents are a major constraint to forage production for livestock in Mongolia. A technical program to identify the magnitude of the problem and strengthen the research capabilities of Mongolian rodent specialists was initiated in 1994. The Brandt's vole is the most widespread and the most detrimental rodent to the steppes of Mongolia. Limited resources inhibit activities by the Mongolian Plant Protection Service to reduce rodent populations. Alternative means to monitor vole activity were developed. Laboratory and field trials showed that voles were susceptible to zinc phosphide treatment and indicated how bait acceptance could be improved.

The Washington Animal Damage Control Program (WADCP) operates within the general structure of the Washington Forest Protection Association. The general goal of the WADCP is to resolve wildlife damage issues in an economically feasible and socially acceptable manner. The four components of the WADCP are program management and administration; support of individual member activities; research, monitoring, and surveys; and promotional and educational activities. An overview of each of these components is provided.

Mountain beaver are a primitive rodent species endemic to the Pacific Northwest and California. In Oregon and Washington, mountain beaver are managed as a pest species due to the damage they inflict to Douglas-fir seedlings as well as 10- to 15-year-old trees. Available biological information on the mountain beaver is limited, thus hampering the ability of managers to develop new tools and techniques to reduce damage. We conducted a series of studies to increase our knowledge of mountain beaver biology and the influence of environmental attributes and stand management practices on demographics. Although mountain beaver damage Douglas-fir and western red cedar seedlings, observations suggest that these tree species are not preferred forage. In one pen study, pens void of preferred vegetation (i.e., salal and sword fern) had significantly more damage than pens with additional forage. Damage did not occur when animals were allowed access to pens with preferred forage, even with increased population pressure. In addition to pen trials, we radio-collared 62 mountain beaver in 3 different harvest units, which varied in vegetation management and stand age, to assess movements and seedling damage. Home ranges were larger on the chemically prepared site with reduced forage than on the non-treated site. Although mountain beaver can inhabit older timber stands, home ranges were relatively large in such stands because of the reduced preferred forage in closed-canopy habitats (3.66 ± 1.49 ha). Once units were harvested, population size increased and home range size decreased (0.88 ± 0.27 ha). Seedling damage and reproductive success were only slightly related to available forage, which was in turn affected by site preparation. Information on home range use, habitat requirements, and the difference in carrying capacity for mountain beaver under varying site preparations, can assist managers in manipulating habitats in order to minimize colonization and reduce seedling damage. We suggest several integrated pest management strategies to minimize seedling damage by mountain beaver.

Deer (Odocoileus spp.) occur across the United States and provide many desirable recreational and aesthetic opportunities. Unfortunately, deer foraging, particularly where population densities are high, can negatively impact agricultural resources or damage ornamental plants. Repellents are often regarded as a desirable approach to limit deer browsing. Although many products are marketed for use as repellents, the efficacy of these products in actually reducing deer browsing is varied. This paper reviews the results from efficacy tests we have conducted at the NWRC Olympia Field Station over the past several years as well as repellent work conducted by others. General efficacies of delivery systems and active ingredients incorporated in a variety of products are compared. Generally, products which have repeatedly demonstrated good efficacy in our trials are those products that produce sulfurous odors. These products have significantly reduced deer browsing for 8 to 12 weeks.

Efforts to establish tree seedlings on sites infested with high populations of pocket gophers (Thomomys spp.) can be futile unless population control measures are implemented. Fumigants are a possible means to reduce pocket gopher populations although the efficacy of fumigants on reforestation sites has been minimal. We conducted a series of experiments to monitor the movement of carbon monoxide through burrow systems and to assess the potential benefits of a blower system. In the first experiment, carbon monoxide was introduced to an artificial burrow system by burning either one or two gas cartridges concurrently or consecutively. The blower was tried at different speeds for varied durations. Carbon monoxide concentration was monitored with sensors that had a detection range from 0 to 5,000 parts per million. Burning the cartridges without the blower was not effective in distributing carbon monoxide. The most effective fumigant dispersal occurred when the blower was used at a low speed for only the period while a cartridge was burning. Burning two cartridges simultaneously was the most effective burn configuration. Results from a second experiment, using vacated pocket gopher burrows instead of an artificial system, were similar to those recorded for the first experiment. Subsequently, we conducted field trials using a blower to disperse carbon monoxide to reduce pocket gopher populations on reforestation sites. These trials did not demonstrate a reduction in pocket gopher activity. We speculate this was because existing burrow plugs prevented the gas from dispersing through the systems or because pocket gophers rapidly blocked burrows when they detected the gas, thus preventing exposure to lethal gas concentrations.

Black bear damage to commercial, coniferous trees on intensively managed public and private forest lands of the Pacific Northwest continues to be a problem for forest managers. Historically, methods such as relocation or spring hunts have been used in an effort to reduce bear density and damage. More recently, supplemental feeding has been used in an attempt to provide for the nutritional needs of bears during the damage period. Alternative silvicultural practices and repellents are being investigated for their ability to reduce the likelihood of bear damage. These and other methods need to be examined for their effectiveness, especially in light of social attitudes, increasing costs, and legal constraints. As part of an integrated pest management (IPM) approach, there is a need to better define the nature, timing, and extent of tree damage by bears. We review the literature and discuss the results from several studies that help answer some of these questions. Managers and researchers will be continuously challenged to find innovative and publicly acceptable methods to maintain a harmonious and delicate balance between the needs and desires of humans and the needs and propensities of black bears.

Economic losses caused by herbivores and other species that inflict damage by browsing or gnawing are substantial. Because lethal approaches to damage reduction are not always practical or desirable, there is an increase in interest in the development of alternative, non-lethal technologies. Repellents may provide a feasible alternative. Here, we present recent studies of three repellent types: 1) anthranilate derivatives (e.g., methyl anthranilate), 2) predator scents (e.g., coyote urine), and 3) bittering agents (e.g., denatonium saccharide). Anthranilate derivatives and predator odors both appear to be promising repellents. Avoidance of the former substances is based on irritant volatiles, and anthranilates may be especially beneficial when the aim is to prevent gnawing damage. Predator odors may be most applicable for protection of vegetation. The effectiveness of these substances appear to be based on the presence of highly volatile, light molecular weight sulfur compounds. Unlike anthranilates or predator odors, bitter substances are largely ineffective as repellents for herbivores.

Black bears forage on Douglas-fir vascular tissue in the spring, and this behavior can be severely detrimental to the health and economic value of a timber stand. Foraging is selective in that not all stands are damaged and, within a stand, one tree may be stripped while its neighbor is ignored or minimally sampled. A series of studies was conducted to assess whether bear selectivity is affected by chemical constituents within vascular tissue, and whether these constituents are affected by silvicultural practices. The results are interpreted to identify forest practices that may alleviate damage, or at least predict where damage is most likely to occur.

Nutria were introduced from South America to the United States in the 1930s for fur farms and, due to releases and escapees, are currently established in 15 states. Nutria are important to the Louisiana fur industry, but they also cause extensive damage to coastal marsh ecosystems when populations are high. Louisiana uses an incentive program for hunters and trappers during trapping season (winter), which helps to control the fast-growing nutria populations. While this approach is effective, additional management tools are needed to control nutria year-round and over large areas. Other tools for nutria control include toxicants, baits and lures, and multiple-capture traps. In this study, we evaluated nutria responses to olfactory cues in a Y-maze that potentially could be used as lures in traps or bait stations. Three olfactory cues were selected more frequently than others: Nutria #1 (apple-based commercial lure), nutria gland secretion, and female nutria fur extract. We also evaluated attention by nutria to two species of fertilized and non-fertilized marsh plants that potentially could be used as lures in multiple-capture traps on coastal marsh. Nutria did not show a strong preference for either plant species, but they gave significantly more attention to fertilized plants than non-fertilized plants or soil treatments. Results with nutria urine were equivocal. The materials identified in this study show potential for the development of additional tools to manage nutria populations and their impacts on coastal marsh ecosystems.

The mountain beaver is a fossorial rodent species endemic to the Pacific Northwest and portions of California. This herbivore is managed as a pest species because of the impact it has on newly planted Douglas-fir seedlings. Currently, managers are limited to trapping for population control; however, in Washington trapping has been further curtailed by anti-trapping legislation. Presently there are no registered underground toxicants for mountain beaver control. We have documented the efficacy of chlorophacinone, presented in daily doses, as a possible alternative for mountain beaver control. Daily baiting would be unreasonable and costly alternative for timber managers, so we conducted a series of tests to determine if a single or double baiting was efficacious. In addition, we tested the caching behavior of the mountain beaver when offered bags of oats. This behavior may help reduce impacts to non-target species as well reduce environmental exposure and degradation. Mountain beaver readily cached bags of chlorophacinone within their artificial burrows, and efficacy of a one-time and two-time dose was 100%. We determined that even with the highest chlorophacinone residuals (0.354 ppm) that the risk quotient for mink and red-tailed hawk was exactly at the level of concern that EPA recognizes for endangered and threatened species.