The Heithaus lab has been involved in research on sea turtles since 1997. Initial studies began in Shark Bay, Western Australia and has now expanded to several locations in the Caribbean Sea. Studies on turtles have focused on the role of predation risk from large sharks like tiger sharks in shaping their behavior, the effects of environmental factors on diving behavior, foraging ecology, individual specialization in behavior, and the roles of sea turtles in seagrass ecosystems.
As part of the Shark Bay Ecosystem Research Project (SBERP), the focus has been understanding the foraging ecology of both green and loggerhead turtles, the risk that each species faces from tiger sharks, the influence of food distribution and tiger shark predation risk on turtle habitat decisions, and influences of water temperature and predation on turtle diving behavior – especially the distribution of their food and risk from tiger sharks.
In the course of these studies, the lab has taken the opportunity to investigate the dynamics of turtle populations in a system free of large human impacts and have undertaken studies of long-term movements of loggerhead turtles. The lab has collected data on turtle abundance within both shallow and deep sampling zones since 1998 and by the end of 2008 had made more than 1,500 passes through these zones. Click here for more on SBERP turtle studies.
AVEDs were first deployed in 1999 to gather detailed data on turtle diving, foraging, and social behavior. Beginning with the deployment of National Geographic’s Crittercam on both green and loggerhead turtles (1999-2004), the lab now uses several types of custom-built systems that feature a video camera (some using GoPro cameras) and a Wildlife Computers MK-10 time depth recorder that can record the GPS position of the turtle at every surfacing.
To gain long-term insights into turtle diving behavior that’s impossible with AVEDs, the lab began deploying time-depth recorders (TDRs) in 2005. The tiny packages include the TDR, an acoustic transmitter, which works through water up to 1000 m, and a VHF transmitter, which works through air up to 20+ km, set in syntactic foam. The combination allows the lab to find the turtle during 5-7 day deployments to identify which habitats they use.
In 2005, the Heithaus lab teamed up with the Department of Environment and Conservation (DEC) and the Yadgalah Aboriginal Corporation to attach satellite transmitters to three female and two male loggerhead turtles. The tags gave daily positions (with an accuracy of 100s of meters) for the turtles for up to a year. The study is ongoing, with nine additional transmitters attached, to help shed light on previously unknown movements and behaviors of male turtles on and between foraging grounds and their breeding grounds.
Sea turtle research in the Caribbean
In 2014, the lab started working on juvenile green turtles on Abaco, Bahamas. The lab is using large cages that keep turtles from grazing in particular areas to determine whether and how turtles are important in determining what species of seagrass – and how much – is found in particular habitats. The lab is also conducting surveys to see whether turtle numbers in an area are driven by the quantity and quality of seagrasses. In early 2015, the lab will begin deploying turtle-cams on several species around Guadaloupe and Dominica as part of larger studies of these ecosystems.