Coltman D W, Bowen W D, Iverson S J, Boness D J
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Physiol Zool. 1998 Jul-Aug;71(4):387-99. doi: 10.1086/515418.
The energy expenditure of breeding male harbour seals, Phoca vitulina, on Sable Island, Nova Scotia, was investigated by measuring changes in body mass, body composition, and water flux using isotope dilution. Seals lost 0.47% +/- 0.04% (n = 34) of their initial mass per day during the breeding season (4 wk), and fat, water, and protein accounted for 64.3% +/- 4.8%, 27.8% +/- 3.3%, and 6.9% +/- 1.4% of this mass loss, respectively (n = 31). Total energy expenditure was estimated as 33.3 +/- 1.9 MJ d(-1), or 3.9 +/- 0.2 W kg(-1) (n = 17), similar to rates measured in terrestrially mating pinniped species. However, unlike terrestrially mating pinnipeds, male harbour seals did not fast during the breeding season, and energy intake from foraging accounted for 61.8% +/- 4.0% of the total energy expended. Males derived most of their expended energy from food intake early in the breeding season. However, as oestrus females became increasingly available, reduced rates of food intake in males were coupled with increased rates of total energy expenditure. Larger males expended significantly more energy from body stores and more total energy than smaller males. Male harbour seals appeared to balance the energetic costs of reproduction against the constraints of small body size by foraging during deep-diving trips before the appearance of oestrus females and by opportunistic feeding throughout the breeding season while at sea. We suggest that size dimorphism may be less pronounced in aquatically mating pinnipeds partly because the temporal and spatial separation of foraging and reproduction is less distinct than it is for terrestrially breeding pinnipeds.
通过使用同位素稀释法测量体重、身体组成和水通量的变化，对新斯科舍省黑貂岛上繁殖期的雄性港海豹（Phoca vitulina）的能量消耗进行了研究。在繁殖季节（4周），海豹每天体重下降0.47%±0.04%（n = 34），其中脂肪、水和蛋白质分别占体重下降的64.3%±4.8%、27.8%±3.3%和6.9%±1.4%（n = 31）。总能量消耗估计为33.3±1.9 MJ d⁻¹，即3.9±0.2 W kg⁻¹（n = 17），这与在陆地交配的鳍足类物种中测得的速率相似。然而，与陆地交配的鳍足类动物不同，雄性港海豹在繁殖季节并不禁食，觅食摄入的能量占总消耗能量的61.8%±4.0%。雄性在繁殖季节早期消耗的能量大多来自食物摄入。然而，随着发情期雌性海豹越来越多，雄性的食物摄入量减少，同时总能量消耗率增加。体型较大的雄性比体型较小的雄性从身体储备中消耗的能量显著更多，总能量消耗也更多。雄性港海豹似乎通过在发情期雌性海豹出现之前的深潜觅食之旅中觅食，以及在整个繁殖季节在海上时进行机会性进食，来平衡繁殖的能量成本与小体型的限制。我们认为，在水生交配的鳍足类动物中，体型二态性可能不太明显，部分原因是觅食和繁殖在时间和空间上的分离比陆地繁殖的鳍足类动物要小。
