Ecological Correlates of Home Range Size

The spatial scales at which individuals exhibit a localizing tendency in their movement behavior can vary widely, even among closely related species. Not surprisingly, home range size is correlated with body size in many animal groups. The energetic requirements of endotherms generally scale in proportion to M0"75, where M is the body mass of a species, and therefore it might be expected that home range size would scale in a similar manner. However, recent analyses have shown that home range size scales as M10, indicating that home range size increases more rapidly with body size than would be expected from simple metabolic considerations (Figure 2, solid line). One explanation is that as a result of increased difficulty of defending large home ranges, home range overlap increases with increasing body size, scaling as M~0'25. When combined with the scaling of metabolic rate with body size (M~0'75), this results in the observed scaling of home range size as M10. Evidence in support of this explanation comes from the fact that while home range size scales as M10, per individual area, the inverse of population density, scales as M0"75 (Figure 2, dashed line). This difference between these two relationships is consistent with the notion of increasing home range overlap in larger-sized animals.

Another important factor influencing animal home range size is its diet. Losses associated with the capture, digestion, and utilization of resources result in a marked reduction in the availability of food resources per unit area at higher trophic levels and consequently home range is strongly affected by trophic level: as the relationships plotted in Figure 2 illustrate, home range sizes of omnivores are approximately 10-15 times higher than those of equivalently sized herbivores, and the home range sizes of predators are 25-60 times higher than that of equivalently sized herbivores. While body size and trophic level account for a significant amount of observed variation in animal home range size, it is also important to note that there is a 1000-fold level of variation around the relationships plotted in Figure 2, emphasizing the fact that the characteristic home range size of a particular species is significantly influenced by a variety of behavioral and ecological factors other than its body size and trophic level.

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