Time partitioning favors the coexistence of sympatric crab-eating fox (Cerdocyon thous) and pampas fox (Lycalopex gymnocercus).

DI BITETTI, M. S.; DI BLANCO, Y. E.; PEREIRA, J. A.; PAVIOLO, A.; JIMÉNEZ PÉREZ, I.

JOURNAL OF MAMMALOGY

Allen Press Associates

Año: 2009 vol. 90 p. 479 - 490

0022-2372

The crab-eating fox Cerdocyon thous and the pampas fox Lycalopex gymnocercus are 2 South American foxes very similar in body size and food habits. Their distribution ranges overlap extensively, which brings the opportunity to conduct comparative studies and understand what mechanisms favor their coexistence. Camera-trap records of both species obtained at the Iberá Nature Reserve (INR), NE Argentina, were used to test the hypothesis that, when living in sympatry, they reduce competition by using different habitats and by being active at different times. Camera-trap records obtained at 2 additional sites inhabited by only 1 of these species, the Atlantic Forest of Misiones (AF) and Lihué Calel National Park (LCNP), were used to compare the activity patterns of these foxes when living alone or in sympatry. At INR, 41 camera-trap stations were set in 2 habitats, 1) shrubland forest and 2) flooded grassland, and in 2 treatments per habitat (a) with and (b) without cattle. Additionally, 3 stations were set in gallery forests. Sampling effort was 1,521 camera-trap days. 540 photographs of crab-eating fox (289 records) and 175 photographs of pampas fox (115 records) were obtained. At LCNP 27 camera-trap stations were set, totaling 1,002 camera-trap days and 109 records of pampas foxes. At AF 195 camera-trap stations (11,689 camera-trap days) provided 103 records of the crab-eating fox. At INR, crab-eating foxes were more frequently recorded in forest habitats than the pampas fox, which preferred opened grasslands. However, both species were found in all habitats and their recording rates were not negatively correlated. At INR, the crab-eating fox was nocturnal, with peaks of activity after dusk and before dawn, a pattern similar to that observed in AF and elsewhere. At INR, the pampas fox showed a peak of activity between 0000 and 0400 h and another one between 1000 and 1300 h, a pattern that is different from that observed at LCNP and other places, where the species is mostly nocturnal. At INR, the pampas fox reduces its activity at time intervals when the activity of the presumably dominant crab-eating fox is high, which may facilitate their coexistence. Time partitioning seems to be an important mechanism that allows the coexistence of these fox species.