Grant: 20-016R
Project Title: Establishing baseline demographics for a globally important loggerhead rookery: Year 1
Project Manager: Sarah Hirsch and Justin Perrault
Organization: Loggerhead Marinelife Center (Non-Profit Organization)
Grant Amount: $35,355.00
Completion Date: 2021-06-08

Summary: Clutch frequency (i.e., the number of nests a female lays within a season) and remigration interval (i.e., the number of years females take off between nesting seasons) are important demographic parameters that must be defined to more accurately estimate sea turtle population size. Despite representing a crucial component in evaluating species abundance, clutch frequency estimates are not well defined. Recent advancement in technologies, such as GPS-linked satellite telemetry, has highlighted the pitfalls of using traditional mark-recapture data to evaluate these parameters, which has in some cases overestimated populations by nearly two-fold. While satellite telemetry has been used to establish clutch frequency and nest site fidelity for loggerheads nesting elsewhere in Florida, no attempts have been made to estimate these parameters for the southeastern Florida loggerhead aggregation. The beaches Loggerhead Marinelife Center (LMC) monitors (~15 km) comprise ~12% of Floridaís total loggerhead nesting activity, despite accounting for just 1% of the stateís monitored coastline. Therefore, LMC monitored beaches are home to the highest loggerhead density in the state, and possibly the world. Yet, little is known about the demographics of this aggregation. Here, we request funds to satellite track seven loggerheads nesting on Juno Beach, Florida in 2020, with the long-term goal of tracking 30 individuals over the course of three to five years. Nesting females will be outfitted with satellite transmitters early in the season to ensure all nesting events are documented and accurate assessment of clutch frequency and nest site fidelity for this globally important loggerhead rookery are established.

Results: Seven nesting loggerhead turtles were outfitted with Wildlife Computers SPLASH tags in April 2020. These turtles were all tagged within the first two weeks of loggerhead nesting on the east coast of Florida to ensure each female was tagged on her first nesting event of the season. Unfortunately, due to COVID-19 restrictions a tablet could not be purchased for evaluating the female's tracking progress in real-time in the field. However, this was purchased this year to be used on the Year 2 turtles tracked in 2021. A UHF receiver was successfully used to reencounter three of the turtles on subsequent nesting events. One turtle was seen once, one of them was seen twice, and the third turtle was seen four additional times. Samples were able to be obtained on each of those re-encounters. Many of the turtles nested outside of LMC's survey area and were therefore not able to be re-encountered, although one of the loggerheads that we did not re-counter was seen by Florida Leatherbacks Inc. when she nested within their nightly survey area. With the tracking data received we were able to ground-truth each of the subsequent encounters with the Fastloc GPS and haul-out data provided by the tags, confirming that the tag data could be used to infer nesting events for each of the turtles that were not able to be reencountered. Clutch frequency ranged from 5 to 8 nests with a mean of 6.1 nests/female. All seven turtles departed for and reached their foraging grounds (two went to the Bahamas and five went to the Mid-Atlantic Bight). Tracking duration lasted from 196 to 393 days. Tracking data has been published on LMC's website.