USDA - APHIS- Wildlife Damage Management

National Wildlife Research Center (NWRC)

Improving Management Strategies to Reduce Damage by Forest and Aquatic Mammals

Methods Development

Nonlethal management approaches depend upon either restricting access to the resource by the offending animal (e.g., physical or behavioral barriers, depleting habitat) or reducing the relative desirability of the protected resource (e.g., repellents, preferred alternative options). Developing nonlethal means to change damaging behaviors necessitates a thorough understanding of the underlying mechanisms that govern foraging behavior. Basic paradigms describing foraging behavior have been developed for experimental species (e.g., rats) and domestic animals (e.g., sheep). However, prior to developing management tools for wildlife based on these paradigms, it is essential to confirm similar behaviors in wildlife species, and to expand our knowledge in pertinent areas.

Often, tools designed to limit wildlife damage rely on certain expected chemosensory responses, but the sensory perception of most wildlife species is virtually unknown. There also is a limited understanding of other factors affecting the usefulness of management tools, such as when and where they are applied, why animals select specific foods or areas to forage, and how animals move and disperse. Effective approaches require specific changes in behaviors of targeted species, and approaches developed and marketed to reduce damaging behaviors often fail because there is a flawed understanding of the biological or behavioral traits of the targeted species.

Nonlethal physical deterrents are effective if they are constructed to completely impede access by offending wildlife. However, construction and maintenance are often cost prohibitive. Less expensive materials and reduced labor costs would be desirable and need to be identified. Necessary strength, size, and configuration must be determined. Further, there is a need to develop an understanding of how these materials affect animals (e.g., attraction) and plants (e.g. microclimate).

Technology has provided a multitude of frightening devices and operating systems (e.g., acoustics, visuals, detection devices), but little is known about how wildlife responses will vary depending on an animal's status (i.e., male vs. female, dominant vs. submissive, individuals vs. group), delivery intervals used with a device, and other factors.

At present, most repellents are ineffective to deter foraging behavior of target species. In fact a preponderance of these substances contain active ingredients to which the target species are indifferent or are offered at concentrations below avoidance thresholds.

Under some circumstances, such as when wildlife populations exceed the capacity of available foraging resources, the only feasible means to protect forest resources is by suppressing specific wildlife populations during periods of vulnerability. Therefore, effective lethal tools (i.e., baits) for pertinent rodent species need to be developed or identified that function in the most humane and environmentally safe means possible.

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Corvallis, OR, Field Station