Multiyear assessment of Crab-eating Fox (Cerdocyon thous) activity patterns in the Brazilian Atlantic Forest

The ecological dynamics of mammalian communities remain poorly known for many of the world’s ecosystems, especially in megadiverse and understudied regions such as the Neotropics. In the case of carnivores, even for relatively common and abundant Neotropical species such as the Crab-eating Fox (Cerdocyon thous), there are still substantial knowledge gaps regarding their ecology and behavior. To address some of these gaps, we performed a 4-year camera-trapping study in a mountainous protected area at the southern limit of the Brazilian Atlantic Forest, aiming to characterize the circadian and circannual activity patterns of C. thous, as well as potential interactions between this fox and other members of the local mammalian community. We obtained 2,213 detections from at least 28 different mammals, with C. thous being the most frequently detected species (n = 675). Our results indicate that C. thous is significantly nocturnal, a pattern that was consistent across the 4 sampled years. We also observed circannual variation in activity patterns during our study, with a significant peak in the Autumn (i.e., between April and June), a finding that contrasts with previous reports from other areas. We also compared its circadian patterns with those from 8 other sympatric mammal taxa, observing varying levels of overlap. An interesting finding was that C. thous circadian activity was significantly associated with the lunar cycle, with the fewest detections observed in the “full moon” phase, a pattern that was also observed in small rodents (i.e., potential prey) and in the felid Leopardus guttulus (a potential competitor). These results shed light on the behavioral ecology of C. thous, strongly supporting a consistent nocturnal activity pattern as also indicated in previous studies, and revealing novel features such as the association with the lunar cycle, which had not been previously reported for this species.