Abstract

ZAPATA, Sonia C. et al. External morphometry and resource partitioning of sympatric foxes (Pseudalopex culpaeus and P. griseus) in southeastern Argentine Patagonia. Mastozool. neotrop. [online]. 2008, vol.15, n.1, pp.103-111. ISSN 0327-9383.

Previous studies have shown that body size of chillas (Pseudalopex griseus) and culpeo (P. culpaeus) foxes was similar when they ocurr allopatrically, whereas a divergence in body size is produced when both species are sympatric. The increase in body size differences between culpeos and chillas toward the southernmost portion of their distribution in Chile and Argentina may favor coexistence by permitting specialization in different food resources. Nevertheless, high trophic overlap between culpeos and chillas has been demonstrated, even under the most extreme body size differences, and it has been postulated that habitat segregation would be the only mechanism promoting coexistence throughout their range. In this work, we study the morphometrics and trophic resource partitioning between culpeos and chillas in an area where the two species are sympatric (northeastern Santa Cruz province in Argentina). In this area, differences in body size between both species were larger than in other sites in Patagonia and northern Chile; the body size of culpeos was even higher than in southern localities. Trophic overlap between culpeos and chillas was intermediate during spring-summer and high during autumn-winter. Our results suggest that trophic resource partitioning is important for the coexistence of both species in northeastern Santa Cruz, which is favored by their body size differences. This pattern is discordant with what it is expected for sympatric foxes in Patagonia.

Keywords : Body size; Niche complementarity; Patagonia; Pseudalopex spp; Trophic segregation.

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