Latitudinal Size Variation of Chilean Foxes: Tests of Alternative Hypotheses

Abstract

There are only 2 species of canids in mainland Chile: the foxes Dusicyon culpaeus and Dusicyon griseus. These 2 species are shown to diverge in body size with increasing latitude: body size of D. culpaeus increases whereas the size of D. griseus decreases south of 33° south latitude (SL). The variables latitude, temperature, annual actual evapotranspiration, and mean size of potential prey species have been previously proposed as correlates of body size in carnivores, but they do not explain the size trends exhibited by the 2 Dusicyon. Instead we found that constancy of mean size of potential prey species throughout the range, and increased habitat overlap between D. culpaeus and D. griseus south of 33° SL, are most likely to explain the size trends of these congeners. Our results suggest a trade—off between habitat and food overlap: progressive increments of interspecific habitat overlap south of 33° SL are compensated by progressively larger differences in body size and in mean prey size.