The principle of competitive exclusion, also known as Gause’s principle, tells us that it is impossible for any two organisms to occupy the same niche without one of them going extinct (Hardin 1960; Gause 1934). This principle is easy to see in frugivores, grainivores, and carnivores that use discrete food packets, such as an insect or seed (Hanley 1982). MacArthur (1958) clearly demonstrated that each species is uniquely adapted to their niche and their competitive advantage prevents niche overlap, with his classic warbler study. However, it is much harder to determine how herbivores partition food resources, since they consume highly variable diets (Hanley 1982). Furthermore, ecosystems are in a state of constant flux, and the addition of non-native animals has the potential to
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Elk have a moderately developed rumen, and they change the composition of their diet depending upon the season and availability of forage. While there is no doubt that elk are intermediate, mixed feeders, they are closer to a grass/roughage eater than they are to a concentrate selector (Hofmann 1988). During most of the year elk forage primarily on graminoids. The broad muzzle of an elk makes it difficult for them to physically select individual plant parts like there smaller cousins, mule deer and white-tailed deer do. However, when elk are compared to a true grass/roughage eater, such as a domestic cow, it becomes apparent that they are much more selective. Mower and Smith (1989) found that the average diet of an elk on winter range in Utah was 61% browse. Similarly, it was reported that the diet of wintering elk in Ontario was over 80% deciduous browse (Jenkins et al. 2007). Yet in other seasons and habitats, elk primarily forage on graminoids. For example, the spring diets of elk in Wyoming were 72% graminoids, and in Alberta winter and spring diets included 95% graminoids (Torstenson et al.
Elk have a moderately developed rumen, and they change the composition of their diet depending upon the season and availability of forage. While there is no doubt that elk are intermediate, mixed feeders, they are closer to a grass/roughage eater than they are to a concentrate selector (Hofmann 1988). During most of the year elk forage primarily on graminoids. The broad muzzle of an elk makes it difficult for them to physically select individual plant parts like there smaller cousins, mule deer and white-tailed deer do. However, when elk are compared to a true grass/roughage eater, such as a domestic cow, it becomes apparent that they are much more selective. Mower and Smith (1989) found that the average diet of an elk on winter range in Utah was 61% browse. Similarly, it was reported that the diet of wintering elk in Ontario was over 80% deciduous browse (Jenkins et al. 2007). Yet in other seasons and habitats, elk primarily forage on graminoids. For example, the spring diets of elk in Wyoming were 72% graminoids, and in Alberta winter and spring diets included 95% graminoids (Torstenson et al.