Population status and demographics of the Texas diamondback terrapin (Malaclemys terrapin littoralis)

2010-2013 - $55,585

George Guillen
Environmental Institute of Houston
University of Houston-Clear Lake


Diamondback terrapins (Malaclemys terrapin) are the only species of turtle that lives exclusively in brackish water. Due to their limited distribution and unique life history the Texas subspecies (Malaclemys terrapin littoralis) may be in danger of local extinction. Various sources of mortality have been identified including habitat loss, crab trap bycatch, power plant intakes, vehicular impacts and boating impacts. Little information has been gathered on the numbers or health of local Texas populations. In late September 2008, Hurricane Ike struck Galveston Bay. The exact impact on the terrapin population is unknown. However, numerous small live and dead juvenile turtles including 8-9 terrapin washed up on Port Aransas/Mustang Island beaches in late 2008 (per T. Amos). These terrapin were weak and two perished. This suggests that many younger terrapin may have been impacted by the hurricane. This proposed research will build upon the 2008-09 work by expanding the scope of the study to adjacent areas within Galveston Bay and adjacent sites to gather additional Texas diamondback terrapin population and demographic data. Our analysis will also include the Deer Island population and additional sites where terrapin have been sighted, including the Anahuac National Wildlife Refuge, West Bay, Brazoria National Wildlife Refuge, Trinity Bay and Christmas Bay, which were not investigated in the previously mentioned study. This study will provide the first comprehensive population estimate of terrapin along the Texas coast and will provide a framework for future population studies.