Bioenergetics and diving activity of internesting leatherback turtlesDermochelys coriaceaat Parque Nacional Marino Las Baulas, Costa Rica

Abstract

SUMMARY Physiology, environment and life history demands interact to influence marine turtle bioenergetics and activity. However, metabolism and diving behavior of free-swimming marine turtles have not been measured simultaneously. Using doubly labeled water, we obtained the first field metabolic rates (FMRs; 0.20–0.74 W kg–1) and water fluxes (16–30% TBW day–1, where TBW=total body water)for free-ranging marine turtles and combined these data with dive information from electronic archival tags to investigate the bioenergetics and diving activity of reproductive adult female leatherback turtles Dermochelys coriacea. Mean dive durations (7.8±2.4 min (±1 s.d.), bottom times (2.7±0.8 min), and percentage of time spent in water temperatures (Tw) ≤24°C(9.5±5.7%) increased with increasing mean maximum dive depths(22.6±7.1 m; all P≤0.001). The FMRs increased with longer mean dive durations, bottom times and surface intervals and increased time spent in Tw≤24°C (all r2≥0.99). This suggests that low FMRs and activity levels, combined with shuttling between different water temperatures, could allow leatherbacks to avoid overheating while in warm tropical waters. Additionally, internesting leatherback dive durations were consistently shorter than aerobic dive limits calculated from our FMRs (11.7–44.3 min). Our results indicate that internesting female leatherbacks maintained low FMRs and activity levels, thereby spending relatively little energy while active at sea. Future studies should incorporate data on metabolic rate, dive patterns, water temperatures, and body temperatures to develop further the relationship between physiological and life history demands and marine turtle bioenergetics and activity.

Comparative Health Assessment of Western Pacific Leatherback Turtles (Dermochelys Coriacea) Foraging Off the Coast of California, 2005–2007

“…However, mean body weights of foraging female leatherbacks in California (512.466.82 kg; 380-607 kg; n513) were significantly higher than those previously reported in nesting adult female leatherbacks in Trinidad (287626 kg; 242-324 kg; n510) and Costa Rica (268644 kg; 196-308 kg; n56), where there was no overlap of ranges (Wallace et al, 2005;Harms et al, 2007). We found a marked distinction between the body condition of foraging and nesting turtles, which likely reflects differences in nutritional status.…”

Energy budget calculations indicate resource limitation in Eastern Pacific leatherback turtles

“…First, we might have underestimated the metabolic cost of activity and thermoregulation in cold temperate waters during migrations and foraging and this could have affected the results of our model. However, as the FMR values we used are the only metabolic rates (MRs) available for free-swimming marine turtles (Wallace et al 2005), they are more appropriate than using nesting MRs. Additionally, according to the gigantothermy model of leatherback thermoregulation, the FMR we used in our calculations (0.74 W kg -1 ) would be adequate -if coupled with appropriate blood-flow adjustments -to maintain a body-core temperature approximately 20°C higher than the ambient water temperature (Paladino et al 1990). …”

“…Given the low metabolic requirements of leatherbacks (Paladino et al 1990, Wallace et al 2005 it is unlikely that starvation has caused recent declines in EP populations. Therefore, while recognizing the speculative nature of our conclusions, we hypothesize that ENSO-related resource limitation might be decreasing EP leatherback reproductive success and increasing risk of incidental capture by fisheries between nesting seasons, thus causing recent (Spotila et al , 2000 and continued (Lewison et al 2004, Kaplan 2005) declines in EP leatherback populations.…”

“…Although the estimated clutch frequency (ECF) was not reported for St. Croix leatherbacks, we assumed that clutch frequencies between the 2 populations were similar because PNMB leatherback ECFs were consistently 1 to 2 nests greater than observed clutch frequencies (OCF) (Reina et al 2002), and the St. Croix OCF was 5.26 (Boulon et al 1996). To estimate energy expenditure during internesting periods, we used the mean field metabolic rate (FMR) (0.40 W kg -1 ) reported by Wallace et al (2005). We estimated travel rates, distances and durations of round-trip migrations as being approximately 4000 km each way at 70 km d -1 for both EP (Morreale et al 1996, Eckert & Sarti 1997, Eckert 2002.…”

“…data) and NA (Ferraroli et al 2004, James et al 2005) populations, and assumed that leatherbacks migrated away from the tropics to high-latitude areas to forage. Because leatherbacks are probably more active and spend more time during migration and foraging in colder waters associated with higher-latitude pelagic areas than in coastal, neritic habitats occupied during the nesting season (James et al 2005), we assumed that the FMR during migration and foraging is closer to the maximum FMR (0.74 W kg -1 ) reported by Wallace et al (2005). We calculated daily maintenance costs while on foraging grounds by assuming that this maximum FMR value included all regulatory processes (e.g.…”