Data from: Energy expenditure of adult green turtles (Chelonia mydas) at their foraging grounds and during simulated oceanic migration

Measuring the energy requirements of animals under natural conditions and determining how acquired energy is allocated to specific activities is a central theme in ecophysiology.
Turtle reproductive output is fundamentally linked with their energy balance so a detailed understanding of marine turtle energy requirements during the different phases of their life cycle at sea is essential for their conservation.
We used the non-invasive accelerometry technique to investigate the activity patterns and energy expenditure (EE) of adult green turtles (Chelonia mydas) foraging year-round at a seagrass meadow in Mayotte (n = 13) and during simulated oceanic migration (displacement from the nesting beach) off Mohéli (n = 1), in the south-western Indian Ocean.
At the foraging site, turtles divided their days between foraging benthically on the shallow seagrass meadow during daylight hours and resting at greater depth on the inner side of the reef slope at night. Estimated oxygen consumption rates (sinline image) and daily energy expenditures (DEE) at the foraging site were low (sinline image during the day was 1·6 and 1·9 times the respective resting rate at night during the austral summer and winter, respectively), which is consistent with the requirement to build up substantial energy reserves at the foraging site, to sustain the energy-demanding breeding migration and reproduction.
Dive duration (but not dive depth) at the foraging site shifted significantly with season (dive duration increased with declining water temperatures, Tw), while overall activity levels remained unchanged. In parallel with a significant seasonal decline in Tw (from 28·9 ± 0·1 °C to 25·3 ± 0·4 °C), there was a moderate (˜19%) but significant decline in DEE of turtles during the austral winter (901 ± 111 kJ day−1), when compared with the austral summer (1117 ± 66 kJ day−1).
By contrast, the turtle moved continuously during simulated oceanic migration, conducting short/shallow dives in the day, which (predominately at night) were interspersed with longer and deeper ‘pelagic’ dives. Estimated oxygen consumption rates during a simulated migration (1·25 ± 0·16 mL O2 min−1 kg−0·83) were found to be significantly increased over the foraging condition, equal to ˜3 times the resting rate at night (0·42 ± 0·02 mL O2 min−1 kg−0·83), and daily energy expenditure amounted to 2327 ± 292 kJ day−1, underlining the tremendous energetic effort associated with breeding migration.
Our study indicates that the accelerometry technique provides a new and promising opportunity to study marine turtle energy relations in great detail and under natural conditions.

测定自然条件下动物的能量需求，并明确获取的能量如何分配至特定生命活动，是生态生理学（ecophysiology）的核心研究主题之一。
海龟的繁殖产出与其能量平衡存在根本性关联，因此深入了解海洋海龟（marine turtle）在海洋生命周期不同阶段的能量需求，对其物种保护至关重要。
本研究采用无创加速度监测技术，针对西南印度洋海域开展两项实验：一是在马约特岛的一处海草床（n=13），对全年在此觅食的成年绿海龟（Chelonia mydas）进行监测；二是在莫埃利岛附近海域，对1只处于模拟远洋洄游状态（即从筑巢海滩驱离）的绿海龟进行监测，以探究其活动模式与能量消耗（energy expenditure, EE）。
在觅食海域，绿海龟的日间活动为在浅海草床进行底栖觅食，夜间则在礁坡内侧的较深水域休憩。觅食海域的估算耗氧率（sinline image）与每日能量消耗（daily energy expenditure, DEE）均处于较低水平：南半球夏季与冬季的日间耗氧率分别为夜间静息代谢率的1.6倍与1.9倍，这与绿海龟需在觅食地积累充足能量储备，以支撑高能耗的繁殖洄游与繁殖活动的需求相符。
觅食海域的潜水时长（而非潜水深度）随季节发生显著变化：潜水时长随水温（water temperature, Tw）降低而延长，整体活动水平则无明显变化。伴随Tw的显著季节性下降（从28.9±0.1℃降至25.3±0.4℃），绿海龟的每日能量消耗在南半球冬季（901±111 kJ·day⁻¹）较夏季（1117±66 kJ·day⁻¹）出现约19%的显著下降。
与之形成鲜明对比的是，模拟远洋洄游状态下的绿海龟始终处于持续移动状态：日间进行短时间浅潜水，夜间则穿插进行更长更深的远洋潜水。模拟洄游过程中的估算耗氧率为1.25±0.16 mL O₂·min⁻¹·kg⁻⁰·⁸³，显著高于觅食状态下的耗氧率，约为夜间静息代谢率的3倍（夜间静息代谢率为0.42±0.02 mL O₂·min⁻¹·kg⁻⁰·⁸³）；此时每日能量消耗达2327±292 kJ·day⁻¹，凸显了繁殖洄游所需的极高能量代价。
本研究表明，加速度监测技术为在自然条件下精细化研究海洋海龟的能量关系提供了全新且极具前景的途径。