Delmarva Fox Squirrel Population Monitoring
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Delmarva Fox Squirrel Populations
Over the past several decades, loss of habitat and development pressure has severely reduced the range of the endangered Delmarva fox squirrel (Sciurus niger cinereus). Delineating current populations and monitoring changes in distribution are necessary components of this species’ recovery, as well as an important consideration when evaluating impacts of development on the Delmarva Peninsula. Presently, trapping is the most commonly used technique to determine the presence of Delmarva fox squirrels in a forest parcel. This method is useful when collecting population data, but is also time, cost and labor intensive.
Alternatives to Trapping
In August 2000, the Chesapeake Bay Field Office initiated an exploratory study to investigate alternative methods to trapping. This study resulted in the creation of an inexpensive, weather resistant hair sampling tube. Hair can be easily removed from the entrapment medium and subjected to DNA analysis. Infrared photomonitors set up with the sampling tubes also provide visual documentation of animal visits. These haircatchers can be used as an alternative to live-trapping to detect the presence of Delmarva fox squirrels, or as a preliminary step to live-trapping when exploring sites where Delmarva fox squirrel occurrence is unknown.
The Chesapeake Bay Field Office completed a pilot study at Blackwater National Wildlife Refuge in order to determine the most effective measurements and entrapment medium for the hair sampling tubes. The prototype resulting from this study was also deployed at Chincoteague National Wildlife Refuge to collect hair from an area with a known Delmarva fox squirrel population. Tubes were distributed at sites with exclusively gray squirrels, and then on sites with both species present. DNA analysis of the hair collected indicated that this is a viable technique for distinguishing gray squirrels from Delmarva fox squirrels.