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Capture and handling may have long-term effects on bears
Wildlife researchers have made great strides in protecting animal welfare and promoting conservation through the study and observation of animals in their natural habitats. While many indirect methods of collecting information exist, such as fecal or hair analyses, some information can be gathered only through the direct capture of animals. A recent article in the Journal of Mammalogy suggests that capture and handling can affect study animals for a longer duration than previously thought.
In this retrospective study, data were compiled from two, previous, independent studies involving two species of bears in geographically distinct areas. The aim of the study was to evaluate whether long-term effects of capture and handling were detectable and, if so, to identify possible implications for the welfare of released animals and the interpretation of research results.
Capture techniques have evolved to be as minimally obtrusive as possible. Some techniques, however, have the potential to cause injury and to change normal behavior and physiology. In many cases, including capture of bears, many animals are not injured and injuries that do occur may not be detected immediately. Long-term study is necessary, therefore, to assess accurately the effects of capture on many wildlife.
The study specifically analyzed the effects of capture and handling on American black bears in the Pisgah Bear Sanctuary in North Carolina and grizzly bears in the Foothills Model Forest in western Alberta, Canada. Researchers captured bears alive using combinations of cushioned leghold snares, remote drug delivery via helicopter, and barrel traps. After capture, bears were anesthetized by remote drug delivery for no more than 75 minutes for observation and sample collection.
About 61% of all bears captured showed abnormally high values for serum muscle enzymes, indicating muscle injury, particularly in bears captured by leghold snares. These enzyme levels could be caused by the stress of capture and the extreme exertion of bears struggling to escape their snares. Captured bears also were prone to decreased mobility after capture. The study found that movement rates were reduced for 3–6 weeks on average before returning to pre-capture rates for both American black bears and grizzly bears. Body condition of bears also tended to decrease over time when bears were captured repeatedly.
In addition to the potential harm to individual bears, the study warns that the accuracy and interpretation of research results on behavior and movements may be affected by capture and handling. While traditionally regarded as an acceptable technique for capture, the use of leghold snares had more adverse effects on the bears studied than did other capture techniques. This method typically requires an animal to be restrained in a snare for an indefinite period of time until the researcher checks the trap, usually once or twice a day. Although the researchers in this study used cushioning devices with leghold snares to minimize injury, the study suggests that these techniques may not adequately reduce the severity of muscle injury caused by exertion of snared bears.
This retrospective study underscores the need to evaluate commonly used capture procedures for wildlife regularly. If snares must be used to capture carnivores, the authors suggest the use of trap-monitoring devices to minimize restraint time and capture-related injury. Additionally, motion-activated video cameras at trap sites would allow researchers to assess animals’ reactions to capture.
“An Evaluation of Long-Term Capture Effects in Ursids: Implications for Wildlife Welfare and Research,” Journal of Mammalogy, Volume 89, Issue 4, August 2008. Published by Allen Press.
Full text of the article is available at http://www.allenpress.com/pdf/mamm-89-04-03_973_990.pdf
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About the Journal of Mammalogy
The Journal of Mammalogy is the flagship publication of the American Society of Mammalogists. Published since 1919, the highly respected international scientific journal promotes interest in mammals throughout the world by the publication of original and timely research on all aspects of the biology of mammals; e.g., ecology, genetics, conservation, behavior, and physiology. To learn more about the society, please visit: http://www.asmjournals.org/
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