Department of Biology and Advanced Facility for Avian Research (AFAR), University of Western Ontario, London, ON, Canada.
Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada.
Oecologia. 2020 May;193(1):67-75. doi: 10.1007/s00442-020-04650-8. Epub 2020 Apr 18.
The extent to which migratory bats forage at stopover sites or while in migratory flight is poorly understood. Endogenous fat stores have lower δC values relative to the dietary substrates from which they were synthesized, and so, the fed versus fasted state of bats should be discernable by comparing their breath δC at capture to that after a known period of fasting. We captured silver-haired bats (Lasionycteris noctivagans) at a stopover site at Long Point, Ontario, Canada, during spring and fall migration. We collected breath samples at capture and after fasting in captivity for 12 h, providing a fasted-state δC value corresponding to metabolism of fat stores. We also collected and weighed fecal pellets produced while in captivity. Breath δC values at capture were positively correlated with mass of feces produced. During spring migration, δC values of breath CO at capture were low and similar to fasting values, but increased with date consistent with increased foraging at stopover and reliance on exogenous dietary nutrients as the season progressed. The opposite temporal pattern was found during fall migration. Our findings suggest that bats forage during migratory stopover when environmental conditions permit despite potential time trade-offs between feeding and travel, and the energy savings resulting from torpor during roosting. This study provides insight into the eco-physiology of bat migration and shows the importance of foraging habitat for migratory bats.
迁徙蝙蝠在中途停留地觅食或在迁徙飞行中觅食的程度还不太清楚。内源性脂肪储存的 δC 值相对于它们合成的饮食基质要低，因此，通过比较蝙蝠在被捕食时的呼气 δC 值与其在已知禁食期后的呼气 δC 值，应该可以分辨出它们的进食状态和禁食状态。我们在加拿大安大略省朗点的中途停留地捕获了银毛蝙蝠（Lasionycteris noctivagans），分别在春季和秋季迁徙期间进行了捕获。我们在捕获时和在圈养中禁食 12 小时后采集了呼气样本，提供了与脂肪储存代谢相对应的禁食状态 δC 值。我们还收集并称重了圈养期间产生的粪便颗粒。捕获时的呼气 δC 值与产生的粪便量呈正相关。在春季迁徙期间，捕获时的呼吸 CO δC 值较低，与禁食值相似，但随着日期的推移而增加，这与在中途停留地觅食的增加以及随着季节的进展对外源饮食营养物质的依赖一致。在秋季迁徙期间发现了相反的时间模式。我们的研究结果表明，蝙蝠在环境条件允许的情况下，会在迁徙中途停留地觅食，尽管在觅食和旅行之间可能存在时间权衡，而且在栖息时打盹可以节省能量。这项研究深入了解了蝙蝠迁徙的生态生理学，并表明了觅食栖息地对迁徙蝙蝠的重要性。
