U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA.
Ecol Appl. 2010 Jan;20(1):251-62. doi: 10.1890/08-1437.1.
Wolves (Canis lupus) in North America are considered obligate predators of ungulates with other food resources playing little role in wolf population dynamics or wolf prey relations. However, spawning Pacific salmon (Oncorhyncus spp.) are common throughout wolf range in northwestern North America and may provide a marine subsidy affecting inland wolf-ungulate food webs far from the coast. We conducted stable-isotope analyses for nitrogen and carbon to evaluate the contribution of salmon to diets of wolves in Denali National Park and Preserve, 1200 river-km from tidewater in interior Alaska, USA. We analyzed bone collagen from 73 wolves equipped with radio collars during 1986-2002 and evaluated estimates of salmon in their diets relative to the availability of salmon and ungulates within their home ranges. We compared wolf densities and ungulate:wolf ratios among regions with differing salmon and ungulate availability to assess subsidizing effects of salmon on these wolf-ungulate systems. Wolves in the northwestern flats of the study area had access to spawning salmon but low ungulate availability and consumed more salmon (17% +/- 7% [mean +/- SD]) than in upland regions, where ungulates were sixfold more abundant and wolves did or did not have salmon spawning areas within their home ranges (8% +/- 6% and 3% +/- 3%, respectively). Wolves were only 17% less abundant on the northwestern flats compared to the remainder of the study area, even though ungulate densities were 78% lower. We estimated that biomass from fall runs of chum (O. keta) and coho (O. kisutch) salmon on the northwestern flats was comparable to the ungulate biomass there, and the contribution of salmon to wolf diets was similar to estimates reported for coastal wolves in southeast Alaska. Given the ubiquitous consumption of salmon by wolves on the northwestern flats and the abundance of salmon there, we conclude that wolf numbers in this region were enhanced by the allochthonous subsidy provided by salmon and discuss implications for wolf-ungulate relations.
北美的狼（Canis lupus）被认为是有蹄类动物的专性捕食者，其他食物资源对狼种群动态或狼猎物关系的影响很小。然而，产卵的太平洋鲑鱼（Oncorhyncus spp.）在北美西北部的狼的整个范围内都很常见，并且可能提供一种海洋补贴，影响远离海岸的内陆狼-有蹄类动物食物网。我们进行了氮和碳的稳定同位素分析，以评估鲑鱼对美国阿拉斯加内陆德纳里国家公园和保护区内的狼的饮食的贡献，该保护区距离潮汐区有 1200 公里的河流。我们分析了 1986 年至 2002 年间佩戴无线电项圈的 73 只狼的骨骼胶原蛋白，并根据鲑鱼在其栖息地范围内的可用性以及有蹄类动物来评估其饮食中鲑鱼的估计值。我们比较了不同鲑鱼和有蹄类动物可利用性地区的狼密度和有蹄类动物与狼的比例，以评估鲑鱼对这些狼-有蹄类动物系统的补贴效应。研究区域西北部平原的狼可以接触到产卵的鲑鱼，但有蹄类动物的可利用性较低，并且消耗的鲑鱼更多（17% +/- 7% [平均值 +/- SD]）比在高地地区多，在高地地区，有蹄类动物的丰富度是前者的六倍，并且狼的栖息地范围内有或没有鲑鱼产卵区（分别为 8% +/- 6%和 3% +/- 3%）。即使有蹄类动物的密度低 78%，西北部平原的狼的数量也仅比研究区域的其余部分少 17%。我们估计，在西北部平原，秋汛的红大麻哈鱼（O. keta）和银大麻哈鱼（O. kisutch）鲑鱼的生物量与那里的有蹄类动物的生物量相当，而鲑鱼对狼饮食的贡献与在阿拉斯加东南部沿海地区报告的狼的估计值相似。鉴于狼在西北部平原普遍食用鲑鱼，以及那里鲑鱼的丰富度，我们得出结论，鲑鱼提供的异源补贴增强了该地区狼的数量，并讨论了对狼-有蹄类动物关系的影响。
