Uncharted Terrapin Territory

terrapin up close

Terrapins don’t have flippers like sea turtles. Instead, they have webbed feet with claws, just like freshwater turtles.

The diamondback terrapin (Malaclemys terrapin) is a turtle species found in coastal marshes, tidal creeks, mangroves, and other brackish or estuarine habitats. Florida is home to five subspecies of diamondback terrapin, three of which occur exclusively in Florida.

Terrapins look similar to their freshwater relatives and can be identified by the black speckles on their neck and legs and the diamond pattern on their shells (carapace). Historically, terrapins were overexploited a century ago, and the species continues to be susceptible to ongoing threats from habitat loss, drowning in crab traps, and other factors that can impact recovery. The diamondback terrapin is currently listed as a Species of Greatest Conservation Need (SGCN), and each subspecies also meets SGCN criteria.

terrapin in grass

Terrapins forage for snails, crustaceans, and other marine or saltmarsh invertebrates.

Little is known about Florida’s diamondback terrapin populations. While they are abundant in a few locations, one subspecies shows evidence of decline, and many locations lack survey data. To improve knowledge of the current status, distribution and trends of terrapins, FWC researchers are working with partners from Flagler College, Florida Department of Environmental Protection, University of Florida, Florida State University, and other institutions to gather data for a biological status assessment of the species statewide.

Beginning in fall of 2015, FWC researchers contacted stakeholders to gather terrapin sighting data to identify priority locations for surveys. Scientists aim to assess at least three significant terrapin populations and evaluate statewide habitat losses associated with human population growth and sea level rise to support development of climate adaptation strategies for species conservation.

FWC scientists and partners are conducting population assessments in locations known to support terrapins. The team is also working with partners to survey areas where population status is unknown to better understand their distribution. Researchers will collect tissue samples for genetic analysis to determine if current subspecies classifications are valid, identify geographic boundaries of distributions, estimate effective population sizes, and assess potential genetic bottlenecks that would suggest recent population declines.

salt marsh

Diamondback terrapins are the only North American turtles that live exclusively in estuaries and brackish habitats such as coastal marshes, tidal creeks and mangrove thickets.

Using the data gathered from partners and statewide surveys, FWC researchers will map the known distribution of terrapins in Florida. A model will be developed which predicts species locations based on characteristics of known inhabited areas to map potential habitat for the species and prioritize areas for future surveys. The model can also be used to evaluate the magnitude of any population reduction that may have occurred, or will likely occur, based on past and projected future habitat changes.

Through 2020, FWC biologists will analyze the data gathered to address the Florida Wildlife Legacy’s goal to fill gaps of unknown information about the diamondback terrapin. Because there is a current lack of knowledge regarding terrapin distributions, population trends, and validity of subspecies designation, these mysteries hinder science and management actions needed to determine the appropriate level of conservation priority. This multi-year project aims to address stakeholder concerns and to develop conservation recommendations which establish meaningful and measurable population management goals for diamondback terrapins in Florida.