Greenland Institute of Natural Resources, Strandgade 91, 2, DK-1401 Copenhagen, Denmark.
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, USA.
Biol Lett. 2023 Feb;19(2):20220423. doi: 10.1098/rsbl.2022.0423. Epub 2023 Feb 22.
Successful foraging is essential for individuals to maintain the positive energy balance required for survival and reproduction. Yet, prey capture efficiency is poorly documented in marine apex predators, especially deep-diving mammals. We deployed acoustic tags and stomach temperature pills in summer to collect concurrent information on presumed foraging activity (through buzz detection) and successful prey captures (through drops in stomach temperature), providing estimates of feeding efficiency in narwhals. Compared to the daily number of buzzes (707 ± 368), the daily rate of feeding events was particularly low in summer (19.8 ± 8.9) and only 8-14% of the foraging dives were successful (i.e. with a detectable prey capture). This extremely low success rate resulted in a very low daily food consumption rate (less than 0.5% of body mass), suggesting that narwhals rely on body reserves accumulated in winter to sustain year-round activities. The expected changes or disappearance of their wintering habitats in response to climate change may therefore have severe fitness consequences for narwhal populations.
成功觅食对于个体维持生存和繁殖所需的正能 量平衡至关重要。然而，海洋顶级捕食者，特别是深潜哺乳动物的捕食效率记录不佳。我们在夏季部署了声学标签和胃温丸，以同时收集关于假定觅食活动（通过蜂鸣检测）和成功猎物捕获（通过胃温下降）的信息，从而估计独角鲸的摄食效率。与每日蜂鸣次数（707 ± 368）相比，独角鲸在夏季的摄食事件日频率特别低（19.8 ± 8.9），并且只有 8-14%的觅食潜水是成功的（即有可检测到的猎物捕获）。这种极低的成功率导致每日食物消耗率极低（低于体重的 0.5%），这表明独角鲸依靠冬季积累的体储备来维持全年的活动。因此，它们冬季栖息地预期的变化或消失可能对独角鲸种群产生严重的适应后果。
