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The Science Seminar Series: Octpober 22, 2009
Diamondback Terrapins: Problems and Solutions
Dr. Joseph Butler
Department of Biology
University of North Florida, Jacksonville, FL
Powell HallTime: 4:00 -5:00pm
Diamondback terrapins (Malaclemys terrapin) range from Cape Cod Bay south to Corpus Christi, Texas. I have studied them for nearly 15 years, most of the time in Florida. During my first year I was fortunate to discover an important nesting beach near Jacksonville, and for several years thereafter, my students and I visited the beach daily during nesting season (1 May through 31 October) to search for new nests. Most nests are deposited in May and June, and hatching begins in July and continues through October. Finding nests on the day they were deposited allowed us to determine the incubation (emergence) period. When we captured females on the beach we recorded demographic data. We determined clutch size by x-raying captured gravid females and by counting eggs in deposited nests. When kept overnight for the x-ray process, the terrapins often defecated allowing us to evaluate their diet by fecal analysis. We found that they ate a mostly tiny clams and small crabs. We determined that over 80% of the nearly 500 nests per year are taken by predators, mostly raccoons. One year a graduate student did a raccoon removal study and found that nest predation decreased significantly. One of the major problems facing terrapin populations throughout their range is that they die in crab traps. We did a three-year study around the state of Florida to test by-catch reduction devices (BRDs), which limit the size of terrapin that can enter the traps. This precludes adult females from entering. We found the ~ 70% of terrapins captured in our study could have been prevented from entering if BRDs were employed. We are currently lobbying the FWC for a regulation that would require BRDs on all crab traps.