Diamondback Terrapin Status Assessment

By Traci Castellón

The diamondback terrapin (Malaclemys terrapin) is a once common estuarine turtle that experienced serious declines a century ago and has declined further in recent decades due to numerous pressures including habitat loss and drowning in crab traps. The Florida coastline represents approximately 20% of the species range and is home to five of seven subspecies, three of which occur only in Florida. However, little is known about the status and distribution of diamondback terrapins in Florida.

Ornate diamondback terrapin (M.t. macrospilota)

With funding from a State Wildlife Grant, FWRI is collaborating with partners statewide to conduct a biological status assessment of the diamondback terrapin in Florida. The project includes population assessments in three locations with known terrapin populations (Banana River, Florida Bay and the middle Florida Keys), and, where possible, we are also helping facilitate population assessments and surveys by partners elsewhere in the state.

Another major component of the work is collection of tissue samples from terrapins statewide for a genetic analysis to assess validity of the currently recognized subspecies taxonomy and, where possible, to conduct population-level genetic analyses to assess effective population sizes, gene flow and possible signs of inbreeding depression. Other efforts include gathering and consolidating existing data from partners to update the known distribution of terrapins statewide and using these data to develop a spatial model to quantify habitat availability. Finally, we will estimate the magnitude of past and future population reductions based on historic and projected future habitat losses.

East coast Florida diamondback terrapin (M.T. tequesta)

To date we have developed numerous partnerships, mapped > 5,500 individual sightings, collected > 300 tissue samples for genetic analysis, completed one season of mark-recapture work in the Banana River, and will begin fieldwork in Florida Bay and the Florida Keys in November 2018.

Major partners include Eastern Florida State College; Sanibel-Captiva Conservation Foundation; the US Geological Survey’s Wetland and Aquatic Research Center; University of Florida’s Department of Wildlife Ecology and Conservation, Florida Sea Grant Extension, Nature Coast Biological Station, and Florida Museum of Natural History; Florida Department of Environmental Protection’s Indian River Lagoon and Tomoka Marsh Aquatic Preserves; North Florida Land Trust; Florida Audubon; Flagler College; Brevard Zoo; and FWC’s Fisheries Independent Monitoring, Habitat and Species Conservation Section, and Florida Keys Wildlife Environmental Area; as well as many dedicated volunteers, students and citizen scientists.

Ornate diamondback terrapin (M.t. macrospilota)

Please send diamondback terrapin sightings to Traci.Castellon@MyFWC.com.