CONICET | Buscador de Institutos y Recursos Humanos

Niche partitioning is a common mechanism by which sympatric mammal carnivorespecies mitigate competition and achieve coexistence. This ecological process isusually measured along three axes: diet, space, and time. The Pampas fox (Lycalopex gymnocercus) and the crab-eating fox (Cerdocyon thous) have similar morphologies and diets and share a wide area of sympatry in South America. Weconducted a large camera-trap survey (~25 000 km2, 234 stations, 10 494 cameratrap days) in the subtropical savannas of Argentina to understand if the crab-eatingfox and the Pampas fox have a competitive coexistence, which would be evidencedby spatial and temporal avoidance. We predicted that the smaller and less socialPampas fox would avoid, either spatially or temporally, the presumably dominantcrab-eating fox. To study habitat associations, we used single-species occupancymodels. We used two-species occupancy models to assess if the Pampas fox has alower probability of occurrence (w) or detection (p) at locations occupied by thecrab-eating fox. We used circular statistics to evaluate if the Pampas fox becomesmore diurnal in areas with high w of the nocturnal crab-eating fox. These foxesshowed different habitat associations. The Pampas fox had lower w in forest habitat. The crab-eating fox had higher w at locations with more wetlands. Both foxeshad higher w at locations with cattle. The w and p of the Pampas fox were notnegatively affected by those of the crab-eating fox, and there was no indication ofspatial avoidance. Contrary to our prediction, the Pampas fox did not become morediurnal at locations with high w of the crab-eating fox. The coexistence of thesespecies seems to be facilitated by their similarity in body weight, which reducesthe chances of intraguild killing, coupled with their divergent niches, which is evidenced in their different habitat preferences within shared landscapes.

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