Influência antrópica sobre a probabilidade de ocupação de mamíferos carnívoros e as relações interespecíficas entre predadores e suas presas na Caatinga brasileira

Abstract

The habitat loss and modification, directly or indirectly related to human activities, represent a serious threat to mammal populations around the world. The situation in Caatinga is no different. Characterized by low humidity rates for most of the year, this semi-arid biome is exposed to high anthropogenic impact rates, such as extensive livestock farming, hunting, introduction of exotic species and the continuous expansion of wind farms in preserved areas. In this regard, carnivorous mammals, one of the most vulnerable animals to landscape modifications, are widely threatened. Land use can also induce behavioral adaptations in wild species and this might have implications for interspecific relationships. Predators use space in a way that maximizes their foraging success. They occupy locations where the prey is most prevalent or vulnerable. However, small carnivores also have to deal with conflicting demands between adjusting their activities according to the occurrence of prey and avoiding agonistic encounters with larger predators. In this study we use camera traps to evaluate the occupancy probability of carnivores in relation to distances to settlements, wind farms and watercourses in a priority area for the conservation of biodiversity in the Caatinga. Similarly, we explore how the occurrence of domestic dogs, hunters and cattle affect the occupancy probability of wild carnivores. We also investigate whether the occurrence of prey and dominant competitors, such as the ocelot Leopardus pardalis, and top predators (puma Puma concolor and jaguar Panthera onca) influence the distribution, detection and daily activity patterns of two small neotropical felids, the northern tiger cat (Leopardus tigrinus) and the jaguarundi (Puma yagouaroundi). The frequency of use of the ocelot was lower in the ranches near the settlements. The probability of use of the jaguar was negatively correlated with the distance from the wind farm, while the detection was positively correlated with this covariate. We found a positive correlation between the jaguarundi occupancy and the distance to wind farms. We found higher probabilities of puma and jaguarundi occupancy and ocelot detection in sites near water. The wild dog occupancy positively correlated with the presence of poachers. We also identified greater odds of crab-eating fox detection in the sites mostly frequented by cattle. In general, and as expected, different species exhibited distinct response patterns to human influences in the study area. The occupancy probability of the northern tiger cat correlated positively with the presence of Spixs cavy (w+ = 0.91) and negatively with the presence of the ocelot (w+ = 0.75). The occurrence of the rock cavy was an important predictor of the detection of the northern tiger cat (w+ = 0.50). The occurrence of Spix's cavy was the only covariate that influenced the occupancy of the jaguarundi (w+ = 1.00). The probability of detection of this feline was also correlated positively with the occurrence of the top predators (w+ = 0.50). The coefficient of temporal overlap between the northern tiger cat and the two smaller prey species (the cavies) was high (1 > 0.75). The northern tiger cat also presented a high degree of temporal overlap with the ocelot (1 = 0.74) and top predators (1 = 0.76). In the case of the jaguarundi, there was considerable overlap with the agouti (1 = 0.76). However, the predominantly diurnal activity pattern of this feline was reflected in low temporal overlap with the other species, of both prey and predator. Our data suggest that prey wields more influence than top predators on habitat use and activity pattern of the small felids. However, the ocelot seems to have strong influence on small felines, especially on the northern tiger cat, which tends to spatially segregate itself. Overall, our study indicates that the carnivores are exposed to a number of human origin disturbances and that conservation measures should be taken to ensure the continuation of these species, specially those that are more sensitive and threatened.