Globally, large carnivores are declining due to direct persecution, habitat loss, and prey depletion. The effects of prey depletion could be amplified by changes in the composition of the herbivore (prey) community that provoke changes in carnivore diets, but this possibility has received little attention. We tested for changes over the past half‐century in prey selection by the large carnivore guild in Zambia's Kafue National Park (KNP). Across 52 predator–prey dyads, 71% of the observed changes showed that large prey have become less important and small prey have become more important. Consequently, dietary niche breadth has decreased for KNP carnivores and niche overlap has increased. We tested whether changes in the importance of prey species are related to their current abundance and uniformly found that prey that have increased in importance are now relatively common, while those that have decreased in importance are now relatively rare. We identify four potential effects of these changes for conservation (through intraguild competition, group size, the energetics of hunting, and vulnerability to snaring) that warrant investigation. Synthesis and applications. Patterns of prey selection by the large carnivores in Kafue National Park (KNP) have changed appreciably over the past half‐century. Decreased predation on large prey, which are now relatively rare, has caused niche compression and increased overlap in carnivore diets. Predation by all KNP large carnivores now concentrates on four small prey species that remain relatively abundant (impala, puku, lechwe, and warthog). Methods to detect such changes in interactions between species are well‐established, but are rarely applied to large carnivore‐ungulate systems. To guide conservation of ecosystem function, monitoring programmes should consider whether prey depletion alters the patterns of predation or competition within the predator guild because these interactions strongly affect the distribution and abundance of both predators and prey. If the patterns seen in KNP are general, then where carnivores are limited by prey depletion, conservation efforts will be most effective if they focus on mitigating the loss of large prey. In KNP, targeted efforts to protect prey larger than 200 kg, particularly buffalo, should be a priority.
While trophy hunting provides revenue for conservation, it must be carefully managed to avoid negative population impacts, particularly for long-lived species with low natural mortality rates. Trophy hunting has had negative effects on lion populations throughout Africa, and the species serves as an important case study to consider the balance of costs and benefits, and to consider the effectiveness of alternative strategies to conserve exploited species. Age-restricted harvesting is widely recommended to mitigate negative effects of lion hunting, but this recommendation was based on a population model parameterized with data from a well-protected and growing lion population. Here, we used demographic data from lions subject to more typical conditions, including source-sink dynamics between a protected National Park and adjacent hunting areas in Zambia's Luangwa Valley, to develop a stochastic population projection model and evaluate alternative harvest scenarios. Hunting resulted in population declines over a 25-yr period for all continuous harvest strategies, with large declines for quotas>1 lion/concession (~0.5 lion/1,000 km ) and hunting of males younger than seven years. A strategy that combined periods of recovery, an age limit of ≥7 yr, and a maximum quota of ~0.5 lions shot/1,000 km yielded a risk of extirpation <10%. Our analysis incorporated the effects of human encroachment, poaching, and prey depletion on survival, but assumed that these problems will not increase, which is unlikely. These results suggest conservative management of lion trophy hunting with a combination of regulations. To implement sustainable trophy hunting while maintaining revenue for conservation of hunting areas, our results suggest that hunting fees must increase as a consequence of diminished supply. These findings are broadly applicable to hunted lion populations throughout Africa and to inform global efforts to conserve exploited carnivore populations.
Packer et al. reported that fenced lion populations attain densities closer to carrying capacity than unfenced populations. However, fenced populations are often maintained above carrying capacity, and most are small. Many more lions are conserved per dollar invested in unfenced ecosystems, which avoid the ecological and economic costs of fencing.
U.S. wolf-hunting policies do not align with ecological theory or data
If access to food is affected by the risk of predation, then the number of individuals killed by predators is an incomplete measure of the limiting effect of predation. Nonetheless, it is often assumed that the costs of antipredator responses (risk effects) are either small enough to be ignored or positively correlated with direct predation, and thus unlikely to alter inferences based on predation rates. These assumptions are rarely tested. Here we studied five large carnivores and ten prey species in three Zambian ecosystems to test relationships between direct predation, antipredator vigilance and trade-offs with foraging. The presence of a predator caused vigilance to increase by a factor of 2.4, with substantial variation among prey species in the strength of this response. This was associated with a 28% decrease in the proportion of individuals foraging, a trade-off that was consistent across species. We detected no correlation between direct predation and the strength of antipredator responses, which undermines the gambit of ignoring risk effects. The strength of antipredator responses was uncorrelated with broad attributes of predators and environments, but was correlated with attributes of prey. Responses were stronger for small species and for browsers/mixed feeders relative to grazers. It has previously been noted that small ungulates face higher rates of direct predation. Building on this inference, our results suggest that carnivore loss/restoration will also have stronger behaviorally-mediated effects on small ungulates, particularly browsers and mixed feeders. If such species increase their representation where carnivores are depleted, then cascading effects on vegetation would be expected.
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