Small-mammal consumption by sympatric canids in southern Brazil: niche overlap and prey selection

Maury Sayão Lobato Abreu Abreu, Andressa da Rosa Wieliczko, Alex Mesquita, Emerson M. Vieira


The crab-eating fox, Cerdocyon thous, and the pampas fox, Lycalopex gymnocercus, are two endemic canids from the neotropics that are sympatric in the Rio Grande do Sul State, southern Brazil. Previous studies indicated that both species feed mainly on small mammals, without marked differences between their diets, at least when small-mammal genera are not determined. In the present study, our objective was to evaluate the similarity in diet composition of those foxes, identifying the genera of small mammal consumed. Besides that, we also investigated potential patterns of prey selection by the canids. We analyzed 222 samples of fox feces from the National Park of Aparados da Serra (NPAS) in southern Brazil (29°10’S, 50°05’W) collected from 2000 to 2005. Fox species were determined by identification of hairs found in scats. We also conducted, between 2000 and 2002, a survey of small mammals using capture-mark-recapture techniques. Our results indicated that the species studied do not differ significantly in relation to the small mammals they consume. We also detected that both canids seem to prefer feeding on rodents of the genus Akodon. On the other hand, rodents of the genus Oligoryzomys were consumed less than would be expected. Our results indicated that prey similarity is very high for the studied canids, even under a more refined analysis of small-mammal preys. This pattern supports the suggestion that niche differentiation between C. thous and L. gymnocercus probably occurs through other mechanisms than diet (e.g. habitat or activity time).

Key words: araucaria forest, cerdocyon thous, rodents, feeding habits, niche overlap, lycalopex gymnocercus.

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