Interspecific competition and the geographical distribution of red and Arctic foxes Vulpes vulpes and Alopex lagopus
Hersteinsson P., Macdonald DW.
The goegraphical distribution of red and arctic foxes differ. The hypothesis that this difference results directly from their relative adaptations to extreme cold is dismissed. Consideration of body size and biogeographic effects on productivity suggests that the northern limit of the red fox's geographic range is determined directly by resource availability (and thus ultimately by climate), whereas the southern limit of the arctic fox's range is determined, through interspecific competition, by the distribution and abundance of red fox. -from Authors