Evaluating potential tagging effects on leatherback sea turtles

Abstract

Although the use of satellite tracking to study the leatherback sea turtle Dermochelys coriacea continues to increase, there has been little inquiry into the effects of this research. We inves- tigated effects of handling and tagging on leatherbacks using state-space estimated positions from 42 turtles satellite-tagged at sea. Although a control group was not available, we observed several pos- sible effects of tagging and handling. Turtles were much more likely to begin migration, and travel speeds were significantly higher in the first week after capture. We inferred that 17 of the 42 turtles departed Canadian waters immediately after tagging. Turtles were more likely to begin their migra- tion immediately if they were tagged later in the year, or if they were tagged following entanglement in fishing gear. Turtles that remained in the north commenced foraging after a median of 12.7 d. We also documented reports of previously harnessed leatherbacks re-sighted on nesting beaches. Although it remains uncertain whether the observed effects are due to capture and/or tagging and whether they are detrimental to individual turtles, this study emphasizes the necessity of considering tag effects on this species.