阿拉斯加棕熊对三文鱼的食用:营养需求与杀婴风险之间的权衡?
Consumption of salmon by Alaskan brown bears: a trade-off between nutritional requirements and the risk of infanticide?
作者信息
Ben-David Merav, Titus Kimberly, Beier LaVern R
机构信息
Department of Zoology and Physiology, University of Wyoming, P.O. Box 3166, Laramie, WY 82071, USA.
出版信息
Oecologia. 2004 Feb;138(3):465-74. doi: 10.1007/s00442-003-1442-x. Epub 2003 Dec 13.
The risk of infanticide may alter foraging decisions made by females, which otherwise would have been based on nutritional requirements and forage quality and availability. In systems where meat resources are spatially aggregated in late summer and fall, female brown bears (Ursus arctos) would be faced with a trade-off situation. The need of reproductive females to accumulate adequate fat stores would likely result in a decision to frequent salmon streams and consume the protein- and lipid-rich spawning salmon. In contrast, aggregations of bears along salmon streams would create conditions of high risk of infanticide. We investigated consumption of salmon by brown bears on Admiralty and Chichagof Islands in Southeast Alaska from 1982 to 2000 using stable isotope analysis and radiotelemetry. While nearly all males (22 of 23) consumed relatively large amounts of salmon (i.e., >10% relative contribution to seasonal diet), not all females (n=56) did so. Five of 26 females for which we had reproductive data, occupied home ranges that had no access to salmon and thus did not consume salmon when they were mated or accompanied by young. Of females that had access to salmon streams (n=21), all mated individuals (n=16) had delta(15)N values indicative of salmon consumption. In contrast, 4 out of 16 females with cubs avoided consuming salmon altogether, and of the other 12, 3 consumed less salmon than they did when they were mated. For 11 of 21 females with access to salmon streams we had data encompassing both reproductive states. Five of those altered foraging strategies and exhibited significantly lower values of delta(15)N when accompanied by young than when mated, while 6 did not. Radiotelemetry data indicated that females with spring cubs were found, on average, further away from streams during the spawning season compared with females with no young, but both did not differ from males and females with yearlings and 2-year-olds. Females with young that avoided salmon streams were significantly lighter indicating that female choice to avoid consumption of salmon carries a cost that may translate to lower female or cub survivorship. The role of the social hierarchy of males and females, mating history, and paternity in affecting the risk of infanticide and foraging decisions of female brown bears merit further investigation.
杀婴风险可能会改变雌性的觅食决策,否则这些决策原本会基于营养需求、食物质量和可获得性。在夏末和秋季肉类资源在空间上聚集的系统中,雌性棕熊(Ursus arctos)将面临一种权衡局面。繁殖期雌性积累足够脂肪储备的需求可能会导致它们决定频繁前往鲑鱼溪流并食用富含蛋白质和脂质的产卵鲑鱼。相比之下,沿着鲑鱼溪流聚集的熊会创造出高杀婴风险的条件。我们利用稳定同位素分析和无线电遥测技术,调查了1982年至2000年阿拉斯加东南部金钟岛和奇恰戈夫岛上棕熊对鲑鱼的消费量。虽然几乎所有雄性(23只中的22只)都食用了相对大量的鲑鱼(即对季节性饮食的相对贡献>10%),但并非所有雌性(n = 56)都如此。在我们有繁殖数据的26只雌性中,有5只占据的活动范围无法获取鲑鱼,因此在交配或育幼时不食用鲑鱼。在可以进入鲑鱼溪流的雌性(n = 21)中,可以获取鲑鱼溪流的雌性(n = 21)中,所有已交配个体(n = 16)的δ(15)N值表明其食用了鲑鱼。相比之下,16只带幼崽的雌性中有4只完全避免食用鲑鱼,在其他12只中,有3只食用的鲑鱼比交配时少。在可以进入鲑鱼溪流的21只雌性中,我们有11只的数据涵盖了两种繁殖状态。其中5只改变了觅食策略,育幼时的δ(15)N值显著低于交配时,而6只则没有。无线电遥测数据表明,与没有幼崽的雌性相比,春季产崽的雌性在产卵季节平均离溪流更远,但两者与带一岁幼崽和两岁幼崽的雄性和雌性没有差异。避免前往鲑鱼溪流的带幼崽雌性明显更轻,这表明雌性选择避免食用鲑鱼会付出代价,这可能会转化为雌性或幼崽更低的存活率。雄性和雌性的社会等级制度、交配历史以及父系身份在影响雌性棕熊杀婴风险和觅食决策方面的作用值得进一步研究。