Current Research Studies

Gray Squirrel Contraceptive Project

The eastern gray squirrel (EGS) (Sciurus carolinensis) is one of the most common wildlife species in urban and suburban communities within the eastern United States. Because of their relative adaptability and lack of predators in urban environments, their numbers have increased in communities across their natural range. With this increase in numbers there has also been a corresponding increase in human-squirrel conflicts. Most notable is the damage gray squirrels are causing to trees and shrubs in managed landscape settings. Gnawing and stripping of tree bark by gray squirrels has become a serious problem in communities where squirrel populations are unusually high. For example, recent observations by landscaping crews on Clemson University’s main campus have documented over 100 mature trees killed directly by gray squirrels gnawing and bark stripping, and an additional 100 trees severely damaged by squirrels (Bill Carson, personal communication). An outside arborist consultant estimated the loss of one mature tree from gray squirrels on Clemson’s campus to be $13,275.00. Using these estimates, damage caused by gray squirrels on Clemson’s campus may exceed $1.3 million dollars.

Efforts to control EGS numbers and their associated damage have been limited to exclusion techniques, habitat modification, repellents, trapping, shooting, and recreational hunting.  Unfortunately in some situations, these alternatives are not effective, practical, or socially acceptable as tools for controlling EGS numbers and associated problems that they cause in urban and suburban communities. Recent work by Pai (2009) to evaluate the effectiveness of the immunocontraceptive GonaCon™ in reducing reproduction in a small group (317) of EGS on the campus of Clemson University demonstrated that the contraceptive was effective in preventing reproduction in both male and female squirrels. However, the cost of capturing and vaccinating individual EGS with GonaCon™ was $15/squirrel and proved to be cost prohibitive, especially when administering on a large scale basis like the entire campus of Clemson University (325 ha).

This project proposes to field test the DiazaCon™ to reduce EGS reproduction and damage on the entire campus of Clemson University.  Like GonaCon™, DiazaCon™ has been shown to be effective at inhibiting reproduction in a variety of birds and mammals.  An additional benefit of DiazaCon™ is that it is an oral bait and does not require capturing EGS. Consequently is shows great promise as a cost-effective, non-lethal method of controlling EGS reproduction and damage in urban and suburban communities.