Post-release changes in the fine-scale diving behavior and activity of loggerhead sea turtles (Caretta caretta) from the Northeastern Gulf of Mexico

Biologging devices have been used to provide critical insights into the ecology of many animal taxa and are particularly valuable when studying species that are difficult to observe directly, like sea turtles. However, post-release changes in movement and behavior, likely the result of capture, handling, and tag attachment, can introduce biases that need to be accounted for when analyzing the data obtained from tag deployments. Fortunately, recent advancements in biologging devices allow not only for horizontal movements to be monitored at high resolution, but vertical movements as well, often in concert with behavioral data collected by integrated cameras. These types of data allow for rigorous assessment of post-release effects on study subjects. Here, we investigated short-term changes in loggerhead sea turtle (Caretta caretta) behavior following capture and release in the Northeastern Gulf of Mexico, Florida, U.S.A, using tags equipped with high-definition cameras, pressure sensors and tri-axial accelerometers to record movement and diving behavior at sub-second resolutions. We used a generalized additive model framework to identify non-linear temporal changes in sea turtle behavior following release. Longer handling times were associated with more frequent, shorter dives and more swimming. These dive characteristics were also seen immediately following release. Dive activity (dynamic body acceleration) was nearly twofold higher immediately following release relative to when it had stabilized, suggesting greater energy expenditure. However, these behavioral effects were relatively short lived. Diving frequency and activity decreased over time as dives became longer and the probability of observing individuals foraging and resting increased. However, we found that the time it took for behaviors to stabilize to what might be considered more natural varied substantially depending on the behavior considered. As such, investigators should carefully consider how behaviors of interest change after release to avoid biases in interpretation, rather than just excluding data before a pre-defined cutoff. Our data contribute to a growing literature investigating the effects of capture and handling on post-release behavior of tagged animals across a variety of taxa and highlight the need to consider behaviors separately. This will help to limit biases when interpreting tagging data and serve to fine tune tagging methods to improve animal welfare.