Effects of helicopter capture and handling on movement behavior of mule deer


Research on wildlife movement, physiology, and reproductive biology often requires capture and handling of animals. Such invasive treatment can alter behavior, which may bias results or invalidate assumptions regarding representative behaviors. To assess the impacts of handling on mule deer (Odocoileus hemionus), a focal species for research in North America, we investigated pre‐ and post‐recapture movements of collared individuals, and compared them to deer that were not recaptured (controls). We compared pre‐ and post‐recapture movement rates (m/hr) and 24‐hour straight‐line displacement among recaptured and control deer. In addition, we examined the time it took recaptured deer to return to their pre‐recapture home range. Both daily straight‐line displacement and movement rate were marginally elevated relative to monthly averages for 24 hours following recapture, with non‐significant elevation continuing for up to 7 days. Comparing movements averaged over 30 days before and after recapture, we found no differences in displacement, but movement rates demonstrated seasonal effects, with faster movements post‐ relative to pre‐recapture in March and slower movements post‐ relative to pre‐recapture in December. Relative to control deer movements, recaptured deer movement rates in March were higher immediately after recapture and lower in the second and third weeks following recapture. The median time to return to the pre‐recapture home range was 13 hours, with 71% of deer returning in the first day, and 91% returning within 4 days. These results indicate a short period of elevated movements following recaptures, likely due to the deer returning to their home ranges, followed by weaker but non‐significant depression of movements for up to 3 weeks. Censoring of the first day of data post‐capture from analyses is strongly supported, and removing additional days until the individual returns to its home range will control for the majority of impacts from capture. © 2014 The Wildlife Society.

Journal of Wildlife Management