Fine-Scale Dive Profiles and Activity Patterns of Sea Turtles in the Gulf of Mexico

Science Center Objects

Researchers are developing acceleration data logger pop-off packages that can be affixed to sea turtles to collect behavioral patterns of diving, surfacing, and general activity levels.

 

The Science Issue and Relevance: As part of the Gulf of Mexico Marine Assessment Program for Protected Species (GoMMAPPS), USGS and the Bureau of Ocean Energy Management (BOEM) are collaborating to better understand sea turtle diving behavior in the Gulf of Mexico. Despite the impressive body of research available on sea turtle movements, little is known about their fine-scale activities and behavior. Satellite tags log dive data, but only provide relatively coarse depth-bin data summaries. The fine-scale dive profiles and activity budgets for these imperiled species are critical, especially where dredging operations occur.

Loggerhead sea turtle (Caretta caretta)

Loggerhead sea turtle (Caretta caretta) (Credit: Andrew Crowder)

 

Acceleration data loggers (ADLs) provide a way to assess turtle behavior at a much finer scale than dive data alone, allowing scientists to empirically measure body movements and orientation. The high-resolution data collected by an ADL can be used to identify and quantify specific behaviors (e.g., various types of swimming behavior based on their flipper-beat frequency and amplitude). When coupled with ADL- collected environmental data (e.g., depth and temperature) and location data collected from an attached satellite tag, ADL data is particularly informative. However, an ADL poses a logistical challenge because the logger stores information to memory; in order to obtain the data, the ADL must be recovered directly from the animal.

 

Methodology for Addressing the Issue: To gather finer-scale data on dive profiles for immature and mature endangered Kemp’s ridleys and threatened loggerheads of both sexes, we are developing a pop-off package that can be retrieved at-sea after a defined period of time attached to the animal. Pilot testing will occur in the researcher’s regular sea turtle field sites in Florida (i.e., Biscayne Bay, Dry Tortugas National Park, Everglades National Park, St. Joseph State Park).

 

Satellite tags have been deployed on sea turtles captured as part of a relocation trawling project associated with coastal dredging in the Gulf of Mexico. These trawling operations will be used to tag sea turtles with the ADL pop-off package and collect biological samples to inform management decisions related to trawling and dredge operations. Data collected from the ADL will be analyzed to decipher behavioral patterns of diving, surfacing, and general activity levels. This will be paired with location data derived from satellite tags to interpret animal movement patterns in specific locations, characterize dive profiles and areas used by sea turtles throughout the year, and identify and assess physical and biological features of high-use habitats, especially those that overlap with proposed BOEM dredging sites.

sea turtle with pop off package

A sea turtle is released with an acceleration data logger pop-off package affixed to its carapace. (Credit: David Roche)

Future Steps:  This work lays the foundation for a long-term capture-mark-recapture study to determine turtle abundance and distribution in critical segments of the Gulf of Mexico study area. These data will advance the knowledge of what sea turtles are doing in the marine environment, where they are often unobservable to humans. Research results will be widely disseminated through reports to BOEM, presentations at regional and local conferences and peer reviewed publications.

 

Combining fine scale dive information with genetic analyses, population demographics, health, and foraging studies will allow BOEM to address information gaps as identified through the National Environmental Policy Act (NEPA) process and Endangered Species Act (ESA) Section 7 consultations.  These data could be used to inform management decisions related to protected species monitoring, decommissioning activities, and significant sediment resource extraction mitigation operations.

 

Related Project(s) and Product(s):

Kemp's Ridley sea turtle forage location centroids in the northern Gulf of Mexico, 2010, 2011 and 2012. https://www.sciencebase.gov/catalog/item/58e298d5e4b09da67996a84f