The bat-eared fox: A dietary specialist?

We studied the degree of dietary specialisation of bat-eared foxes (Otocyon megalotis) by analysing 177 scats collected on a game ranch in central South Africa. Bat-eared foxes generally are considered to be insectivorous with a distinct specialisation on termites, however, our results indicated a much broader and opportunistic diet. Termites were detected in more than 90% of the scats throughout the year, but they only contributed 12–40% to the ingested biomass across seasons. Instead, fruits, primarily bluebush (Diospyros lycioides), were the most important food category in summer (63% biomass) as well as in autumn (74% biomass). Also, high niche breadth values (B = 5.7–6.9 for frequency of occurrence, B = 1.8–4.1 for biomass data) indicated a rather generalistic feeding behaviour. We also documented numerous cases of opportunistic scavenging on carcasses by bat-eared foxes. The difference with earlier dietary studies of bat-eared foxes might be attributable to geographical and ecological variations among sites and also partly to methodological differences. Concerning the latter, no previous studies considered biomass calculations but instead most assessed the frequency of occurrence of prey items, which likely overestimated the importance of small prey such as termites.     

Seasonal patterns of habitat selection in the insectivorous bat‐eared fox

Understanding how animals utilize their habitat provides insights about their ecological needs and is of importance for both theoretical and applied ecology. As changing seasons impact prey habitat selection and vegetation itself, it is important to understand how seasonality impacts microhabitat choice in optimal foragers and their prey. We followed habituated bat‐eared foxes (Otocyon megalotis) in the Kalahari, South Africa, to study their seasonal habitat selection patterns and relate them to the habitat preferences of their main prey, termites (Hodotermes mossambicus). We used Resource Selection Functions (RSFs) to study bat‐eared foxes’ 3rd‐ and 4th‐order habitat selection by comparing used locations to random ones within their home ranges. Third‐order habitat selection for habitat type and composition was weak and varied little between seasons. We found that patterns of fox habitat selection did not mirror habitat selection of Hodotermes (quantified using RSFs), even when feeding on them (4th‐order). Taken together, these results might indicate that bat‐eared foxes’ food resources are homogenously distributed across habitats and that prey other than Hodotermes play an important role in bat‐eared foxes’ space use.     

Genetic structure,spatial organization,and dispersal in two populations of bat‐eared foxes

We incorporated radio‐telemetry data with genetic analysis of bat‐eared foxes (Otocyon megalotis) from individuals in 32 different groups to examine relatedness and spatial organization in two populations in South Africa that differed in density, home‐range sizes, and group sizes. Kin clustering occurred only for female dyads in the high‐density population. Relatedness was negatively correlated with distance only for female dyads in the high‐density population, and for male and mixed‐sex dyads in the low‐density population. Home‐range overlap of neighboring female dyads was significantly greater in the high compared to low‐density population, whereas overlap within other dyads was similar between populations. Amount of home‐range overlap between neighbors was positively correlated with genetic relatedness for all dyad‐site combinations, except for female and male dyads in the low‐density population. Foxes from all age and sex classes dispersed, although females (mostly adults) dispersed farther than males. Yearlings dispersed later in the high‐density population, and overall exhibited a male‐biased dispersal pattern. Our results indicated that genetic structure within populations of bat‐eared foxes was sex‐biased, and was interrelated to density and group sizes, as well as sex‐biases in philopatry and dispersal distances. We conclude that a combination of male‐biased dispersal rates, adult dispersals, and sex‐biased dispersal distances likely helped to facilitate inbreeding avoidance in this evolutionarily unique species of Canidae.     

Microhabitat preferences of longear sunfish: low light intensity versus submerged cover

Both cover and light intensity are important factors in microhabitat selection of fishes, suggesting a possible hierarchical relationship. Many centrarchids have been shown to prefer low light intensities and heavy submerged cover, but adult nonbreeding longear sunfish are reported to occupy sparsely vegetated, clear, shallow water during the brightest part of the day, probably for foraging. To determine the relative importance of cover and light intensity to longear sunfish, we presented nonbreeding adults with choices between these two conditions in a series of three laboratory experiments. Longear sunfish preferred low light to high light intensity and preferred submerged cover to no cover. However, when given a choice, they preferred to occupy low light intensity conditions without cover rather than submerged cover under higher light intensity conditions. Thus, low light intensity, such as is found in greater pool depths, may be the preferred refuge from predation for longear sunfish.     

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

Cape foxes (Vulpes chama) and bat-eared foxes (Otocyon megalotis) are sympatric with black-backed 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 km² for cape foxes, 5.0 km² for bat-eared foxes, and 17.8 km² 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. © 2012 The Wildlife Society.