Conserving large carnivores: dollars and fence.

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km(-2) , unfenced populations require budgets in excess of $2000 km(-2) to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density-independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20-40 years.

Trade-offs of predation and foraging explain sexual segregation in African buffalo.

1. Many studies have investigated why males and females segregate spatially in sexually dimorphic species. These studies have focused primarily on temperate zone ungulates in areas lacking intact predator communities, and few have directly assessed predation rates in different social environments. 2. Data on the movement, social affiliation, mortality and foraging of radio-collared African buffalo (Syncerus caffer) were collected from 2001-06 in the Kruger National Park, South Africa. 3. The vast majority of mortality events were due to lion (Panthera leo) predation, and the mortality hazard associated with being an adult male buffalo in a male-only 'bachelor' group was almost four times higher than for adult females in mixed herds. The mortality rates of adult males and females within mixed herds were not statistically different. Mortality sites of male and female buffalo were in areas of low visibility similar to those used by bachelor groups, while mixed herds tended to use more open habitats. 4. Males in bachelor groups ate similar or higher quality food (as indexed by percentage faecal nitrogen), and moved almost a third less distance per day compared with mixed herds. As a result, males in bachelor groups gained more body condition than did males in breeding herds. 5. Recent comparative analyses suggest the activity-budget hypothesis as a common underlying cause of social segregation. However, our intensive study, in an area with an intact predator community showed that male and female buffalo segregated by habitat and supported the predation-risk hypothesis. Male African buffalo appear to trade increased predation risk for additional energy gains in bachelor groups, which presumably leads to increased reproductive success.

Multi-host pathogens and carnivore management in southern Africa.

A retrospective serosurvey of multi-host feline and canine viruses among carnivore species in southern Africa (n=1018) identified widespread pathogen exposure even in remote protected areas. In contrast to mortality experienced in East African predators, canine distemper virus (CDV) infection among African wild dogs (Lycaon pictus) in Botswana was not associated with identifiable change in pup survivorship or disease related mortality of adults. A disease outbreak of unknown aetiology occurred in the same population over 4 weeks in 1996. Outbreak boundaries coincided with ecotones, not the spatial distribution of contiguous packs, highlighting the potential importance of landscape heterogeneities in these processes. Direct management of pathogens in domestic animal reservoirs is complicated by the apparent complexity of pathogen maintenance and transmission in these large systems. Conservation effort should be focused at securing large metapopulations able to compensate for expected episodic generalist pathogen invasion and attention directed to addressing underlying causes of population depression such as habitat loss and wildlife conflict.