Although many studies employ allometric relationships to demonstrate possible dependence of various traits on body mass, the relationship between home range size and body mass has been perhaps the most difficult to understand. Early studies demonstrated that carnivorous species had larger home ranges than herbivorous species of similar mass. These studies also argued that scaling relations (e.g., slopes) of the former were steeper than those of the latter and explained this in terms of the distribution of food resources, which are more uniformly distributed for most herbivores than for carnivores. In contrast to these studies, we show that scaling relations of home ranges for carnivorous mammals do not differ significantly from those of herbivorous and omnivorous species and that all three exhibit slopes that are significantly steeper than predicted on the basis of energetic requirements. We also demonstrate that home range size is constrained to fit within a polygonal constraint space bounded by lines representing energetic and/or biophysical limitations, which suggests that the log-linear relationship between home range area and mass may not be the appropriate function to compare against the energetically predicted slopes of 0.75 or 1.0. It remains unclear, however, why the slope of the relationship between home range area and body mass, whether based on raw data or on constraint lines, always exceeds that predicted by the energetic needs hypothesis.
The hypothesis that patterns of sex-biased dispersal are related to social mating system in mammals and birds has gained widespread acceptance over the past 30 years. However, two major complications have obscured the relationship between these two behaviors: 1) dispersal frequency and dispersal distance, which measure different aspects of the dispersal process, have often been confounded, and 2) the relationship between mating system and sex-biased dispersal in these vertebrate groups has not been examined using modern phylogenetic comparative methods. Here, we present a phylogenetic analysis of the relationship between mating system and sex-biased dispersal in mammals and birds. Results indicate that the evolution of female-biased dispersal in mammals may be more likely on monogamous branches of the phylogeny, and that females may disperse farther than males in socially monogamous mammalian species. However, we found no support for a relationship between social mating system and sex-biased dispersal in birds when the effects of phylogeny are taken into consideration. We caution that although there are larger-scale behavioral differences in mating system and sex-biased dispersal between mammals and birds, mating system and sex-biased dispersal are far from perfectly associated within these taxa.
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