Interspecific Agonism in Two Parapatric Species of Chipmunks (Eutamias)

Abstract

The chipmunk species Eutamias minimus oreocetes and Eutamias amoenus luteiventris are altitudinally parapatric in the Rocky Mountains of southern Alberta; E. m. oreocetes occupies the alpine, E. a. luteiventris occupies forest. During simultaneous introductions of these subspecies into a large structurally complex arena, E. a. luteiventris was dominant in a majority of matches. During matches in which E. m. oreocetes was introduced 1 day prior to the introduction of E. al luteiventris, both species won the same number of matches. Habitat structure appeared to influence the outcome of interactions. Prior residence of a nonforest habitat may provide E. m. orecetes with sufficient advantage in agonistic interactions to exclude E. a. luteiventris from such habitat. Eutamias minimus borealis and E. amoenus ludibundus are geographically parapatric in the Rocky Mountains of central Alberta, Canada; both species occupy forest habitats. During simultaneous introductions of these subspecies into the arena, E. a. ludibundus was dominant in a majority of matches. A comparison of three studies of interspecific agonism between various subspecies of E. minimus and E. amoenus indicates that E. minimus is generally subordinate to E. amoenus regardless of habitats occupied. The distributions of the four subspecies in Alberta suggest that E. amoenus luteiventris displaced E. minimus borealis from the montane forest of southern Alberta, and E. minimus oreocetes may represent refuge populations of E. minimus borealis that successfully excluded E. amoenus ssp. from the alpine.