McHuron Elizabeth A, Sterling Jeremy T, Costa Daniel P, Goebel Michael E
Joint Institute for the Atmosphere and Ocean, University of Washington, 3737 Brooklyn Ave NE, Seattle, WA 98105, USA.
Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service - NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA.
Conserv Physiol. 2019 Dec 26;7(1):coz103. doi: 10.1093/conphys/coz103. eCollection 2019.
Quantifying metabolic rates and the factors that influence them is key to wildlife conservation efforts because anthropogenic activities and habitat alteration can disrupt energy balance, which is critical for reproduction and survival. We investigated the effect of diving behaviour, diet and season on field metabolic rates (FMR) and foraging success of lactating northern fur seals () from the Pribilof Islands during a period of population decline. Variation in at-sea FMR was in part explained by season and trip duration, with values that ranged from 5.18 to 9.68 W kg ( = 48). Fur seals experienced a 7.2% increase in at-sea FMR from summer to fall and a 1.9% decrease in at-sea FMR for each additional day spent at sea. There was no effect of foraging effort, dive depth or diet on at-sea FMR. Mass gains increased with trip duration and were greater in the fall compared with summer, but were unrelated to at-sea FMR, diving behaviour and diet. Seasonal increases in at-sea FMR may have been due to costs associated with the annual molt but did not appear to adversely impact the ability of females to gain mass on foraging trips. The overall high metabolic rates in conjunction with the lack of any diet-related effects on at-sea FMR suggests that northern fur seals may have reached a metabolic ceiling early in the population decline. This provides indirect evidence that food limitation may be contributing to the low pup growth rates observed in the Pribilof Islands, as a high metabolic overhead likely results in less available energy for lactation. The limited ability of female fur seals to cope with changes in prey availability through physiological mechanisms is particularly concerning given the recent and unprecedented environmental changes in the Bering Sea that are predicted to have ecosystem-level impacts.
量化代谢率以及影响代谢率的因素是野生动物保护工作的关键，因为人为活动和栖息地改变会扰乱能量平衡，而能量平衡对繁殖和生存至关重要。在海象数量下降期间，我们调查了潜水行为、饮食和季节对普里比洛夫群岛哺乳期北海狗（）的野外代谢率（FMR）和觅食成功率的影响。海上FMR的变化部分由季节和行程持续时间解释，其值范围为5.18至9.68瓦/千克（=48）。海狗从夏季到秋季海上FMR增加7.2%，在海上每多停留一天，海上FMR下降1.9%。觅食努力、潜水深度或饮食对海上FMR没有影响。体重增加随行程持续时间增加，秋季比夏季更大，但与海上FMR、潜水行为和饮食无关。海上FMR的季节性增加可能是由于与年度换毛相关的成本，但似乎并未对雌性在觅食行程中增加体重的能力产生不利影响。总体较高的代谢率以及饮食对海上FMR缺乏任何相关影响表明，北海狗在数量下降早期可能已经达到了代谢上限。这提供了间接证据，表明食物限制可能导致了在普里比洛夫群岛观察到的幼崽生长率低，因为高代谢开销可能导致用于哺乳的可用能量减少。鉴于白令海最近发生的前所未有的环境变化预计会产生生态系统层面的影响，雌性海狗通过生理机制应对猎物可用性变化的能力有限尤其令人担忧。
