Data from: Rapid mobilization of abdominal fat in migrating eared grebes

Eared grebes Podiceps nigricollis, like shorebirds and other long-distance migrants, lay down large amounts of fat to power their journeys. To investigate the pattern of how fat and soft tissue might be mobilized, we used grebes killed in migration and applied computed tomography to reconstruct how stores in the chest, thorax, and abdomen were reduced as body weight decreased. Fat and soft tissue were each mobilized at a constant rate through the entire migration. Fat stores in birds embarking on migration were greater in the abdomen than thorax than chest. In contrast to previous studies indicating that abdominal fat was mobilized first, we found that fat from all areas was mobilized concurrently, but that abdominal fat was catabolized at a greater rate. We suggest why this pattern might be advantageous, consider whether inter-depot differences in fat composition might be involved, and note possible energetic consequences. Whether our findings pertain to other obese or long distance migrants remains to be determined.黑颈䴙䴘（Eared grebe，学名Podiceps nigricollis）与鸻鹬类及其他长途迁徙鸟类类似，会蓄积大量脂肪以支撑迁徙飞行的能量需求。为探究脂肪与软组织的动员规律，本研究采集迁徙途中死亡的黑颈䴙䴘样本，通过计算机断层扫描（computed tomography，CT）技术，重构了随体重下降时胸部、胸腔与腹部脂肪储备的消耗动态。在整个迁徙周期内，脂肪与软组织均以恒定速率被动员消耗。迁徙启程时的个体，其腹部脂肪储备量高于胸腔，胸腔又高于胸部。与此前研究提出的“腹部脂肪率先被动员”的结论相悖，本研究发现所有部位的脂肪均同步启动动员，但腹部脂肪的分解代谢速率更快。本研究探讨了该动员模式的潜在进化优势，分析了不同部位脂肪组成差异是否参与调控该过程，并指出了其可能带来的能量学效应。本研究结论是否适用于其他脂肪蓄积型或长途迁徙物种，仍有待进一步验证。