Good neighbours? Determinants of aggregation and segregation among alpine herbivores

Abstract

Interspecific interactions often determine the structure and stability of biotic communities. In low-productivity and highly seasonal environments such as the alpine tundra, most interactions occur during a short, snow-free period. The strength and direction of these interactions are likely to be determined by the availability of resources, particularly among species of the same ecological guild. Understanding how species interact in such environments can provide insights into the conditions that facilitate their coexistence. We determined the potential for interspecific interactions among 3 resident medium-sized mammalian herbivores inhabiting the alpine tundra and investigated how they share available space and resources. Overlap in their respective activity areas indicated that these species were aggregated at a landscape scale, but other mechanisms allowed their coexistence at a finer scale. Their distributions were primarily associated with shorter distances to heterospecifics and, secondly, with habitat features related to shelter and escape from predation. Our results suggest that these species can (and do) coexist by partitioning their ecological niches. Competition is likely not a major factor in structuring these communities; in turn, facilitative mechanisms may allow co-occurrence of these sympatric herbivores in seasonal, low productivity environments.