Hart, Kristen, 2007, Mangrove Terrapin Mark Recapture Study data.Online Links:
U.S. Department of Agriculture - Natural Resources Conservation Service (NRCS) Department of the Interior - U.S. Geological Survey Department of Commerce - National Oceanic and Atmospheric Administration (NOAA) Environmental Protection Agency (EPA) Smithsonian Institution - National Museum of Natural History (NMNH)
727 803-8747 ext 3035 (voice)
727 803-2032 (FAX)
kristen_hart@usgs.gov
Study objectives were to estimate adult survival probablility, capture probablilty, and abundance of terrapins at this study site. This allowed the establishment of the first baseline assessment for mangrove terrapins in the coastal Everglades.
Mark-recapture techniques were used for Diamondback terrapins. Three weeklong sampling trips were made to the Big Sable Creek system to capture, mark, and recapture terrapins. Captures were concentrated in the upper reaches of creeks in the system. On each sampling trip, named creeks and their navigable branches were surveyed systematically for terrapins at AM and PM low tides. Dip nets were used to capture turtles, with the new moon tides providing the best conditions for capture success.
In addition to taking standard morphometric measurements on each turtle and recording a GPS location for each capture and recapture location, we marked each newly captured terrapin in four ways: (1) by notching the marginal scutes in a systematic pattern, (2) by inserting an individually numbered 9-or 10-digit alpha-numeric passively induced transponder (PIT) tag, (3) by taking head-on, dorsal, ventral, and side view photographs for photo-id (with particular emphasis on capturing the unique pattern of each turtle’s plastron), and (4) by taking blood samples to be screened for microsatellite DNA markers which resulted in locus-specific scores for each individual. For consistency, K. Hart performed all the notching, PIT tagging, photographing, and blood sampling throughout the study. We used the redundant marking system to ensure no tag loss or errors in identification. We also used strict, consistent protocols to catalog animals so that the possibility of misidentification would be essentially zero. We re-weighed and re-measured recaptured turtles, and released all new turtles after workup at their original capture site and all recaptured turtles at their recapture location. Additionally, we attached radiotransmitters to a subset of females to conduct short-term tracking in the study site. For analyses, we constructed a unique 5-capture history for each of the 300 terrapins from the capture and recapture data collected on each trip. Each capture history consisted of the seen (1) or not seen (0) record of the individual during each of the five sampling periods.
We marked a total of 300 terrapins. We captured 24 animals in crab pots on the first sampling trip (November 2001), but thereafter captured terrapins only with dip nets.
We used Program MARK and AIC model selection procedures to derive estimates of survival and capture probability. We used JOLLY Model B to estimate population size.
We continued to define population structure and genetics of Diamondback terrapins at Big Sable Creek complex immediately south of Shark River. A total of 300 unique individuals with a male: female sex ratio of 1.2:1.0 have been captured, measured, weighed, PIT tagged and had blood drawn for genetic samples. Initial population size estimate is about 1,415 individuals based on the Schnabel method. We estimated downed log cover in 6 headwater creeks to correlate with terrapin capture locations. Final objectives are to refine this population estimate, better characterize habitat use, and finish analysis of blood samples previously collected for DNA characterization.
Future analysis of mark-recapture data will allow for determination of effects of hurricanes (i. E., Hurricane Wilma, October 24, 2005) on terrapin survival and capture probabilities.
Genetic analysis is continuing for this population to determine hurricane effects on allele frequencies over time.
Person who carried out this activity:
727 803-8747 ext 3035 (voice)
727 803-2032 (FAX)
kristen_hart@usgs.gov
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hhenkel@usgs.gov
Terrapin Mark-Recapture Study
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727 803-8747 ext 3028 (voice)
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U.S. Department of the Interior, U.S. Geological Survey
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