Thompson Ian D, Colgan Patrick W
Forestry Canada, P.O. Box 6028, A1C 5X8, St. John's, Newfoundland, Canada.
Biology Department, Queen's University, K7L 3N6, Kingston, Ontario, Canada.
Oecologia. 1990 Jul;83(4):443-451. doi: 10.1007/BF00317193.
We examined variation in diet choice by marten (Martes americana) among seasons and between sexes and ages from 1980-1985. During this period prey populations crashed simultaneously, except for ruffed grouse (Bonasa umbellus) which was common at the beginning and end of the study, and masked shrews (Sorex cinereus) which were abundant in 1983. Marten were catholic in selection of prey and made use of most available mammalian prey, ruffed grouse, passerine birds, berries, and insects. Diet niche was widest during the latter three years when prey was scare, particularly in late winter. Diet niche breadth was negatively correlated with abundance of all common prey species. Proportion of small prey species in the diet was correlated with absolute abundance of those species, but proportion of some large prey was related to their relative abundance. Diet choice varied among years and among seasons. Berries and insects were common in summer diets while large prey, particularly varying hare (Lepus americanus), were more frequent in winter diet than in summer diet. We found little evidence that any small mammal species was a preferred prey. Sexual size dimorphism between the sexes did not affect prey choice, nor did age. Reduced foraging effort in winter resulted in a wider diet niche only when prey was scarce. The only prediction of optimal foraging models fully supported by our data was a wider diet niche with reduced prey abundance. However, among the three most profitable prey species choice was dependent on the absolute abundance of the most profitable type (varying hare). We suggest that marten primarily forage for large prey but employ a strategy which results in encounters with small prey as well. These small prey are eaten as they provide energy at minimal cost, between captures of large prey.
我们研究了1980年至1985年间美洲貂（Martes americana）在不同季节、性别和年龄之间饮食选择的差异。在此期间，除了在研究开始和结束时常见的披肩榛鸡（Bonasa umbellus）以及1983年数量丰富的美洲鼩鼱（Sorex cinereus）外，猎物数量同时大幅下降。貂在选择猎物方面较为广泛，利用了大多数可获得的哺乳动物猎物、披肩榛鸡、雀形目鸟类、浆果和昆虫。在猎物稀缺的后三年，尤其是冬末，饮食生态位最宽。饮食生态位宽度与所有常见猎物物种的丰度呈负相关。饮食中小猎物物种的比例与这些物种的绝对丰度相关，但一些大猎物的比例与它们的相对丰度有关。饮食选择在年份和季节之间有所不同。浆果和昆虫在夏季饮食中很常见，而大型猎物，特别是美洲兔（Lepus americanus），在冬季饮食中比夏季饮食中更频繁。我们几乎没有发现任何小型哺乳动物物种是首选猎物的证据。两性之间的性大小二态性并不影响猎物选择，年龄也不影响。只有在猎物稀缺时，冬季觅食努力的减少才会导致更宽的饮食生态位。我们的数据完全支持的最优觅食模型的唯一预测是，随着猎物丰度的降低，饮食生态位会变宽。然而，在三种最有利可图的猎物物种中，选择取决于最有利可图类型（美洲兔）的绝对丰度。我们认为，貂主要捕食大型猎物，但也采用一种策略，导致它们也会遇到小型猎物。这些小型猎物在捕获大型猎物的间隙以最小成本提供能量时被吃掉。
