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Long-term capture-recapture research in the Everglades National Park provides baseline information on the Diamondback Terrapin, a species that may be threatened by human disturbances.
The Science Issue and Relevance: Human induced disturbances threaten the viability and persistence of many vertebrate populations, including turtles. With human pressures mounting in all coastal environments, populations of Malaclemys terrapin are no exception, as their coastal range predisposes them to interactions with humans. In many states throughout the Atlantic and Gulf coasts they are listed as a species of special concern, with their overall status remaining unclear. The evaluation of the potential impacts of human disturbances can be aided by studies of populations subject to minimal human activity, so we initiated a study in a protected wilderness site within Everglades National Park (ENP). We sought to address how ecologically and morphometrically different subtropical mangrove terrapins are from their temperate salt marsh relatives. More specifically, we set out to compare the population structure, habitat use, diets, movements, behavior, and genetic profiles of diamondback terrapins from SW FL mangroves to those of better studied populations inhabiting Atlantic and Gulf coast salt marshes. We are also determining whether terrapins in the Big Sable Creek complex belong to the same, or a different, population than those in Florida Bay (FB), the Ten Thousand Islands area, or those in the Key West National Wildlife Refuge (KWNWR). This research will contribute the ecological information necessary to determine the appropriate conservation status for this species in Florida.
Methodology for Addressing the Issue: We are conducting a long-term capture-recapture study in the Big Sable Creek (BSC) complex of ENP, Florida. Additional samples have been collected from Florida Bay and Key West locations to compare to ENP. We are gathering baseline data on mangrove terrapin body size, population structure, sex ratio, injuries, diet, and growth. Blood samples are taken for genetic profiling to be compared against terrapins found in Florida Bay and the Ten Thousand Island area. Isotope samples are collected to examine long-term and seasonal shifts in diet.
Future Steps: As of January 2016 we have captured and marked 688 individual terrapins in the BSC complex (337 males and 351 females). There have been over 1,760 capture events with a 61% recapture rate (1073 recaptures). Analysis of this data allows determination of the demographics, growth rate, and survival of mangrove terrapins. Additionally we have been able to calculate the home range and movements for 36 individuals. Future plans are to continue the capture-recapture study, as well as to begin satellite tagging females to locate nesting sites and further define habitat use. In 2014 a range wide genetics manuscript was published and in 2015 a diet and foraging ecology manuscript was submitted comparing BSC and FB sites. In FY16 we are working on stable isotope analysis of the terrapins and resources from BSC, FB, and KWNWR; and a 10-yr mark-recapture and movement summary manuscript will be completed.
Additional Related Project(s) and Product(s):
Hart KM (2005) Population biology of diamondback terrapins (Malaclemys terrapin): Defining and reducing threats across their geographic range. Ph.D. Dissertation, Duke University, 235 pp.
Below are publications associated with this project.