African wild dogs

Predators of similar size often compete over prey. In semi-arid ecosystems
where water is a limiting resource, prey availability can be affected by water
distribution, which further increases resource competition and exacerbate conflict
among predators. This can have implications for carnivore dietary competition.
Hence, we evaluated the dynamics of food resource competition between African
wild dogs and four competing predators (cheetahs, leopards, lions and spotted
hyaenas) in different seasons and across areas with different waterhole densities
in Hwange National Park, Zimbabwe. We used the frequency of occurrence of prey
items found in predators’ scats to analyse diet composition, overlap and prey
preference. For most predators, kudu was most frequently consumed and
preferred. Low and medium water-dependent prey (medium and small-sized) were
mostly consumed by wild dogs, leopards and cheetahs. Wild dog diet overlap was
high with all predators, particularly with hyaenas and lions. There were no seasonal
differences in the predators diet. The diet overlap of wild dogs with lions was
highest in the low waterhole density area, and wild dog diet composition did not
differ significantly from the diet of lions and hyaenas. In the low waterhole density
area, wild dogs and hyaenas broadened their niche breadth, and predators diet
had a higher proportion of low water-dependent prey. A low density of waterholes
increased food resource competition. However, high density of waterholes, where
there is more prey availability, can increase the aggregation and density of
predators, and hence, increase the risks involved in interspecific competition on
wild dogs. To reduce food resource competition on wild dogs, we propose to conserve larger-bodied prey that are less dependent on water (e.g. kudu,
reedbuck, eland, gemsbok). As the use of water pumping is common practice, we
propose maintaining water management heterogeneity where prey which is less
dependent on water can also thrive.

Within carnivore guilds, dominant competitors (e.g., lions, Panthera leo) are limited primarily by the density of prey, while subordinate competitors (e.g., African wild dogs, Lycaon pictus) have been limited by the density of dominant competitors. Historically, the fitness and population density of subordinate competitors have not been tightly linked to prey density. However, populations of large herbivores have declined substantially across sub-Saharan Africa due to human impacts, and where prey depletion is severe, fitness costs for competitive subordinates may begin to outweigh the benefits of competitive release. Using long-term intensive monitoring of African wild dogs in Zambia’s Luangwa Valley Ecosystem (LVE), we tested the effects of prey depletion on survival and reproduction. We hypothesized that African wild dog fitness would be lower in prey-depleted areas, despite lower lion densities. Our study area included four contiguous regions that varied in protection level, prey density, and lion density. We fit Bayesian Cormack–Jolly–Seber and closed-capture models to estimate
effects on survival and population density, and generalized linear models to estimate effects on reproductive success. We found that the LVE is a stronghold for African wild dogs, with an estimated median density of 4.0 individuals/100 km2. Despite this
high density, survival and reproduction differed among regions, and both components of fitness were substantially reduced in the region with the lowest prey density.
Anthropogenic prey depletion is becoming an important limiting factor for African wild dogs. If prey depletion (or any other form of habitat degradation) becomes severe
enough that its fitness costs outweigh the benefits of competitive release, such changes can fundamentally alter the balance between limiting factors for competitively subordinate species.