PDF(Pubmed)
Abstract：
Wolves (Canis lupus) can exert top-down pressure and shape ecological communities through the predation of ungulates and beavers (Castor spp.). Therefore, understanding wolf foraging is critical to estimating their ecosystem-level effects. Specifically, if wolves are consumers that optimize tradeoffs between the cost and benefits of prey acquisition, changes in these factors may lead to prey-switching or negative-density dependent selection with potential consequences for community stability. For wolves, factors affecting cost and benefits include prey vulnerability, risk, reward, and availability, which can vary temporally. We described the wolf diet by the frequency of occurrence and percent biomass and characterized the diet using prey remains found in wolf scats on Isle Royale National Park, Michigan, USA, during May-October 2019 and 2020. We used logistic regression to estimate prey consumption over time. We predicted prey with temporal variation in cost (availability and/or vulnerability) such as adult moose (Alces alces), calf moose, and beaver (Castor canadensis) to vary in wolf diets. We analyzed 206 scats and identified 62% of remains as beaver, 26% as moose, and 12% as other species (birds, smaller mammals, and wolves). Adult moose were more likely to occur in wolf scats in May when moose are in poor condition following winter. The occurrence of moose calves peaked during June-mid-July following birth but before calf vulnerability declined as they matured. By contrast, beaver occurrence in wolf scat did not change over time, reflecting the importance of low-handling cost prey items for recently introduced lone or paired wolves. Our results demonstrate that the wolf diet is responsive to temporal changes in prey costs. Temporal fluctuation in diet may influence wolves\' ecological role if prey respond to increased predation risk by altering foraging or breeding behavior.
摘要：
狼（Canis狼疮）可以通过捕食有蹄类动物和海狸来施加自上而下的压力并塑造生态群落（Castorspp。).因此,了解狼的觅食对于估计其生态系统水平的影响至关重要。具体来说,如果狼是优化猎物获取成本和收益之间权衡的消费者，这些因素的变化可能导致猎物转换或负密度依赖性选择，并对社区稳定性产生潜在影响。对于狼来说,影响成本和收益的因素包括猎物脆弱性，风险，奖励,和可用性，这可能在时间上有所不同。我们通过发生的频率和生物量百分比来描述狼的饮食，并使用在皇家岛国家公园的狼腹中发现的猎物来描述饮食，密歇根州,美国,2019年5月至10月和2020年。我们使用逻辑回归来估计猎物随时间的消耗。我们预测了具有成本（可用性和/或脆弱性）随时间变化的猎物，例如成年驼鹿（Alcesalces），小牛驼鹿,和海狸（加拿大蓖麻）在狼的饮食上有所不同。我们分析了206片，确定62%的遗骸是海狸，26%为驼鹿，和其他物种的12%(鸟类，较小的哺乳动物，狼）。成年驼鹿更有可能在5月份出现在狼sc中，当驼鹿在冬季后状况不佳时。驼鹿小牛的发生在出生后的6月至7月中旬达到顶峰，但在小牛的脆弱性随着它们的成熟而下降之前。相比之下,海狸在狼scat中的出现并没有随着时间的推移而改变，反映了低处理成本猎物对最近引入的孤独或配对狼的重要性。我们的结果表明，狼的饮食对猎物成本的时间变化有反应。如果猎物通过改变觅食或繁殖行为来应对增加的捕食风险，则饮食的时间波动可能会影响狼的生态作用。
