An alternative technique for the long-term satellite tracking of leatherback turtles

Abstract

The satellite transmitter fixed on a harness was, until a short time ago, the commonly used attachment technique to follow oceanic movements of the soft-shelled leatherback turtle Dermo- chelys coriacea. However, harnesses have recently been reported to have a potential welfare impact during long-term deployments in this species. Here, we present the first long-term (3 mo) monitoring of 2 leatherback turtles tracked with satellite transmitters directly attached to the carapace and compare tracking data with 3 other turtles, that were concurrently satellite-tracked with traditional harnesses. There were significantly more good quality locations recorded for carapace-equipped turtles than for turtles with harnesses, which suggests that the satellite transmitter is better directly fixed to the carapace. The mean locomotor travel rate (i.e. turtle's own motion taking potential current drift into account) for turtles with harnesses was 16% slower (0.50 ± 0.01 and 0.59 ± 0.02 m s -1 , respec- tively) and dives were 12% shorter (23.2 ± 0.8 and 26.3 ± 0.8 min, respectively) than for carapace- equipped turtles, but all were to a similar depth (87.0 ± 3.1 and 80.7 ± 2.9 m, respectively). Despite our small sample sizes, these first results suggest a marked hydrodynamic impact of the harness on the leatherback's swimming and diving capabilities, and stress the need for further developments to improve long-term monitoring while reducing hydrodynamic constraints for this species.