Relationship between home range and population density in mammals: the role of sociality, territoriality and habitat dimensionality

Organisms’ energy requirements increase with body mass, leading to larger home range areas and lower population density. Previous research has highlighted the differential scaling of these variables in mammals, where species with large home ranges have higher density than expected due to increased home range overlap. Here we investigate this phenomenon in mammals, and hypothesize that home range overlap is influenced by group size, territoriality and habitat dimensionality. We address the question from both a correlative and a mechanistic perspective. First, we compiled data on home range, density, group size, territoriality and habitat dimensionality for 319 species. We then estimated average home range overlap, and explained its variation considering average home range, group size, territoriality and habitat dimensionality. We then complement the comparative analysis with a random-encounter mechanistic model (i.e. gas model) – treating individuals or social units as moving particles whose encounter rates depend on density, movement and an effective interaction distance – to provide independent support to the correlative analysis. Our results support previous studies showing that home range overlap with increasing home range sizes. However, this relationship is lower for species with larger group size due to the effect of spatial clumping on the relationship between body mass and group density, and body mass and individual home range area. Furthermore, such a relationship is higher and steeper in non-territorial species and those foraging in tridimensional habitats. The mechanistic model further supports these hypotheses. Taken all together, our results suggest that home range overlap ultimately depends on both species’ area demands and their capacity to monopolize resources. Our study highlights the importance of considering both population density and home range as non-redundant measures of habitat requirements in conservation analyses.