Resource partitioning among cape foxes, bat-eared foxes, and black-backed jackals in South Africa

摘要

Cape foxes (Vulpes chama) and bat-eared foxes (Otocyon megalotis) are sympatric with blackbacked jackals (Canis mesomelas) over much of southern Africa, although competition with and/or predation by jackals may suppress local populations of both fox species. From 2005 to 2008, we captured, radio-collared, and monitored 11 cape foxes, 22 bat-eared foxes, and 15 black-backed jackals on a game ranch in South Africa to investigate their spatial, habitat, temporal, and dietary resource overlap. Mean annual home-range sizes were 27.7 km 2 for cape foxes, 5.0 km 2 for bat-eared foxes, and 17.8 km 2 for jackal family groups. Home ranges overlapped completely between species, although core areas overlapped less (<45%), with cape foxes and jackals overlapping the least (12%). When active, cape foxes, but not bat-eared foxes, used core areas of jackal groups less than expected. Additionally, both fox species used jackal core areas less than expected for their den sites, suggesting areas outside jackal core areas were used as refuges by foxes. Strong levels of habitat partitioning were not apparent at the study site or home-range levels, although habitat selection for den sites differed between jackals and cape foxes. Jackals were the most diurnal across seasons, whereas cape foxes were the most nocturnal. Diets overlapped little (R0 0.20–0.34) among the canid species, with bat-eared foxes overlapping the least with the others. Jackals killed at least 5 collared bat-eared foxes and 1 collared cape fox, indicating potential interference competition, probably for exclusive use of territorial space rather than over shared resources. We conclude that bat-eared foxes coexisted with jackals primarily by their dietary specialization and group living. Cape foxes coexisted with jackals by exhibiting high levels of spatial, habitat, temporal, and dietary partitioning. Surprisingly, the fox species exhibited positive associations with each other. Our results show the mechanisms that may allow jackals to suppress fox populations, yet also show how foxes, in turn, use different mechanisms to coexist with a dominant canid.