Effect of bio-logger attachment and retention on the behavior and welfare of loggerhead and green turtles in captivity

Animal-borne devices (bio-loggers) are widely used in sea turtle research to generate data on free-swimming turtles and their environment. Yet it is rarely acknowledged that handling and/or bio-logger retention can affect the behavior and/or welfare of the tagged animal nor have previous studies attempted to disentangle the individual effects of handling from those of bio-logger retention. To address these issues, we observed and quantified the behavior of 10 loggerhead ( Caretta caretta ) and 7 green turtles ( Chelonia mydas ) in captivity for 4 h each day over a three-day experiment. On day 1 (“control”), turtles were not handled and had no bio-logger attached. On day 2, turtles were handled and a bio-logger was attached. On day 3, turtles were handled and the bio-logger was removed. This experimental set-up enabled comparisons between turtle behavior after handling both with and without bio-logger retention. Loggerhead turtles spent more time swimming after handling but bio-logger retention had no impact on their behavior. On the other hand, green turtles spent less time swimming after handling and also spent 5% of their time scratching or self-grooming when a bio-logger was present. Opportunistically, we also observed that bio-logger and epoxy removal was easier in loggerhead turtles, while it led to superficial carapace lesions in 4 out of 7 green turtles. These results highlight that while both loggerhead and green turtles respond to handling, they do so in different ways. Furthermore, only green turtles appeared to have adjusted their behavior in response to bio-logger retention.