Locomotor activity during the frenzy swim: analysing early swimming behaviour in hatchling sea turtles

Abstract

SUMMARYSwimming effort of hatchling sea turtles varies across species. In this study we analysed how swim thrust is produced in terms of power stroke rate, mean maximum thrust per power stroke and percentage of time spent power stroking throughout the first 18h of swimming after entering the water, in both loggerhead and flatback turtle hatchlings and compared this with previous data from green turtle hatchlings. Loggerhead and green turtle hatchlings had similar power stroke rates and percentage of time spent power stroking throughout the trial, although mean maximum thrust was always significantly higher in green hatchlings, making them the most vigorous swimmers in our three-species comparison. Flatback hatchlings, however, were different from the other two species, with overall lower values in all three swimming variables. Their swimming effort dropped significantly during the first 2h and kept decreasing significantly until the end of the trial at 18h. These results support the hypothesis that ecological factors mould the swimming behaviour of hatchling sea turtles, with predator pressure being important in determining the strategy used to swim offshore. Loggerhead and green turtle hatchlings seem to adopt an intensely vigorous and energetically costly frenzy swim that would quickly take them offshore into the open ocean in order to reduce their exposure to near-shore aquatic predators. Flatback hatchlings, however, are restricted in geographic distribution and remain within the continental shelf region where predator pressure is probably relatively constant. For this reason, flatback hatchlings might use only part of their energy reserves during a less vigorous frenzy phase, with lower overall energy expenditure during the first day compared with loggerhead and green turtle hatchlings.

Swimming ability in sea turtle hatchlings: a comparison between species

“…This study suggests that anaerobic metabolism in flatback hatchlings is similar or slightly higher than that of loggerhead hatchlings, however Pereira et al (2011) showed that swimming effort is relatively lower in flatback turtle hatchlings than in loggerhead turtles hatchlings. This suggests that it is the aerobic component of flatback hatchling swimming effort that is relatively lower in comparison with loggerhead hatchlings.…”

“…In this study I proposed that loggerhead turtle hatchlings would experience intermediate changes in these physiological variables as a result of their moderate swimming effort, whereas flatback turtle hatchlings would experience smaller changes given their relative low swimming effort, as suggested by previous studies (Pereira et al, 2011;Pereira et al, 2012) concentrations at different times during the beach crawl and early stages of the swimming frenzy in hatchling sea turtles Baldwin et al, 1989;.…”

“…I also expected blood lactate concentrations of flatback turtle hatchlings to be lower than loggerhead turtle hatchlings because they are less vigorously swimmers (slower power stroke rate and less frequent power stroking bouts) (Pereira et al, 2011). However, this was not the case, as lactate concentration was not significantly different between the species during the beach crawl and first hour of swimming.…”

“…The intensity of swimming varies between species Pereira et al, 2011). Green turtle (Chelonia mydas) hatchlings are the most vigorous swimmers followed by loggerhead turtle (Caretta caretta) hatchlings, with flatback turtle (Natator depressus) and leatherback turtle (Dermochelys coriacea) hatchlings being less vigorous Pereira et al, 2011;Pereira et al, 2012).…”

“…In this study, I investigate blood lactate, glucose and corticosterone concentration in hatchling turtles through the beach crawl and early swimming frenzy to test the hypothesis that these parameters will vary in a systematic way with the varying exercise intensity of different species. In particular, I predict that loggerhead turtles experience intermediate changes in these physiological variables as a result of their moderate swimming effort and that flatback hatchlings experience the smallest changes because of their relative low swimming effort (Pereira et al, 2011;Pereira et al, 2012).…”