Final Activity Report Summary - HABITAT LOSS - FOXES (Effects of habitat fragmentation on cape foxes in southern Africa)
Although cape foxes (Vulpes chama) are widely distributed in southern Africa, their numbers have been declining in recent years, and current densities appear to be low everywhere. To investigate if habitat fragmentation and/or competition with larger canids negatively affect cape foxes, populations were studied on two study sites in South Africa from 2005 to 2007. Initial results showed that habitat fragmentation did not have a negative impact on cape foxes. Therefore, subsequent research focused on the interactions of cape foxes and larger canids. A total of 19 cape foxes, 42 bat-eared foxes (Otocyon megalotis), and 15 black-backed jackals (Canis mesomelas) were captured, radio-collared, and monitored on a weekly basis on both sites. Predation from jackals was the largest cause of mortality for cape (67 % of deaths) and bat-eared (50 %) foxes. High jackal numbers caused home ranges to increase from 9.2 to 29.1 km2 for cape foxes, and from 3.5 to 7.2 km2 for bat-eared foxes. Both fox species clearly avoided jackal core areas, thus foxes had to range over larger areas to safely find food in areas with high jackal densities. Cape fox densities decreased from 0.13 to 0.03 fox/km2 in the presence of jackals, primarily due to predation and spatial displacement by jackals. Although density of bat-eared foxes was similar on both sites, their group sizes increased from 2.3 to 4.5 foxes/group in the presence of jackals, probably for better protection against predation. There were no negative interactions between cape foxes and bat-eared foxes, only between jackals and the two fox species. It appears that in the absence of large carnivores (e.g. lions (Panthera leo), spotted hyenas (Crocuta crocuta), leopards (Panthera pardus)), black-backed jackals can attain relatively high densities, which results in severe negative impacts on cape foxes and bat-eared foxes.
To determine dietary habitats and niche overlap, during the 'Effects of habitat fragmentation on cape foxes in southern Africa' (HABITAT LOSS - FOXES) project, > 1 300 scats (i.e. droppings) were collected from cape foxes, bat-eared foxes, and black-backed jackals. Results showed that cape foxes consumed mostly rodents (68 % of diet) and hares (10 %), bat-eared foxes consumed mostly insects (38 %) and fruits (42 %), whereas black-backed jackals consumed mostly small antelopes (53 %). Consequently, dietary overlap was relatively low between cape foxes and jackals (16 % overlap) and between bat-eared foxes and jackals (11 %). Thus, competition for food resources probably was not a major factor influencing the strong competition between jackals and foxes. Rather, competition for space and territories likely had the greatest influence on canid interactions. Finally, several survey methods were compared to determine if they successfully estimated abundances of foxes and jackals. Results showed that both scent-station surveys and scat-deposition rates successfully estimated densities of black-backed jackals across three sites, whereas neither method could accurately estimate densities of cape foxes and bat-eared foxes.
To determine dietary habitats and niche overlap, during the 'Effects of habitat fragmentation on cape foxes in southern Africa' (HABITAT LOSS - FOXES) project, > 1 300 scats (i.e. droppings) were collected from cape foxes, bat-eared foxes, and black-backed jackals. Results showed that cape foxes consumed mostly rodents (68 % of diet) and hares (10 %), bat-eared foxes consumed mostly insects (38 %) and fruits (42 %), whereas black-backed jackals consumed mostly small antelopes (53 %). Consequently, dietary overlap was relatively low between cape foxes and jackals (16 % overlap) and between bat-eared foxes and jackals (11 %). Thus, competition for food resources probably was not a major factor influencing the strong competition between jackals and foxes. Rather, competition for space and territories likely had the greatest influence on canid interactions. Finally, several survey methods were compared to determine if they successfully estimated abundances of foxes and jackals. Results showed that both scent-station surveys and scat-deposition rates successfully estimated densities of black-backed jackals across three sites, whereas neither method could accurately estimate densities of cape foxes and bat-eared foxes.