Wednesday, August 5, 2009

PS 48-85: Short and long distance translocations:  Movement and survival in eastern box turtles (Terrapene carolina carolina)

Scott D. Farnsworth, Richard A. Seigel, and Patrick W. Cain. Towson University

Background/Question/Methods

Human development represents a serious threat to wildlife populations through continued habitat loss and incidental mortality from construction activities.  Resource managers responsible for protecting species with legal status or high public profile are faced with difficult decisions on how to best manage populations located in construction zones.  One approach to mitigate mortalities is to relocate individuals.  The effectiveness of translocation for reptiles and amphibians has been questioned, with studies often reporting higher mortality and increased movements of translocated individuals.  Translocations of reptiles and amphibians have primarily involved moving animals long distances, well beyond an individual’s home range.  For reptiles this means finding new nesting, foraging, and overwintering sites, which may be problematic.  Moving individuals only short distances, within their home range, may reduce those problems.  As part of the mitigation plan for a highway construction project in central Maryland, groups of eastern box turtles (Terrapene carolina carolina) were translocated both short distances (<0.5km), and long distances (~5km).  To investigate differences in survival and movement patterns among long distance translocation, short distance translocation, and non-translocation groups, I tracked 94 turtles (31 long distance translocation, 29 short distance translocation, and 34 non-translocation) using radio telemetry.

Results/Conclusions

Eleven animals died during the first activity season after translocation (April through November 2008).   The mortalities included two long distance translocation, six short distance translocation, and three non-translocation animals.  The causes of mortality included road kill, construction activity, and unknown (1, 4, and 6 mortalities respectively).  All construction related mortalities were a result inadequate exclusion fencing to keep turtles from trespassing back onto the construction site.  All mortalities due to construction were either non-translocation or short distance translocation animals.  Eleven other individuals were located at least once within the construction zone, suggesting that without our intervention mortality rates would have been much higher.  Preliminary results for movement show that turtles in the non-translocation group had the lowest average movements while long distance translocation animals had the greatest average movements.  Long distance translocation turtles also chose overwintering sites farther away from their initial overwintering sites than either short distance translocation or non-translocation turtles (average distance from original site of 261.8m, 155.6m, and 124.3m respectively).  This suggests that movement patterns of short distance translocation turtles are more like native turtles.