Anthropogenic activities facilitate temporal overlaps and spatial partitions among sympatric canids in a human-modified landscape of Bulgaria

Mammalian carnivores (order Carnivora) occupy higher trophic levels in many terrestrial ecosystems, shaping community structures via direct predation and trophic cascades. The interference competition among sympatric carnivores (i.e., aggression and killing) has a major role in the intraguild interactions in which the large-dominant predators typically constrain behaviors and resource use patterns by exploitative (i.e., resource) competitions as well as the survival of smaller subordinate species by interference (i.e., direct) competitions. The free-roaming dog, Canis lupus familiaris, has been introduced worldwide and the species affects regional biodiversity, including native carnivore species. Using camera trapping, we investigated the temporal and spatial overlaps between the free-roaming dog and two wild canids, the golden jackal (Canis aureus) and the red fox (Vulpes vulpes), in different landscapes of central Bulgaria. We predict their interference interactions, namely that the dog, as the largest competitor, suppresses the golden jackal with intermediate body size, and, in turn, the golden jackal suppresses the smaller red fox. In mountainous forest landscapes where the free-roaming dog was absent or scarce, the golden jackal and red fox partitioned their diel activities, while there were moderate levels of spatial overlap. In agricultural lowlands where dogs were abundant and anthropogenic disturbances were relatively high, all three canids were primarily nocturnal with high temporal overlap, probably owing to human activities (e.g., hunting) in the daytime. The golden jackal was spatially separated from the dog, whereas the red fox spatially overlapped with large dogs. Our results indicated that, in human-modified landscapes with scattered forests and shrubs, spatial partitioning between the free-roaming dog and the golden jackal at fine spatial scales facilitates their sympatry by decreasing the probability of direct encounters. Furthermore, our findings also indicate that spatiotemporal interactions between the golden jackal and the red fox can change in association with various human disturbances, e.g., landscape modifications, human activities, and the introduction of dogs.