Angela Gaylard

Compensatory life‐history responses of a mesopredator may undermine carnivore management efforts

Summary 1. Lethal carnivore management, aimed at reducing carnivore impacts, is a global phenomenon threatening the persistence of many carnivores. Black-backed jackals Canis mesomelas, the dominant cause of livestock predation in southern Africa, are widely hunted to reduce livestock predation. Despite centuries of lethal management, jackals persist. Smaller canids, like jackals, are highly adaptable and display variable responses to mortality sources, which may affect management outcomes. 2. The effects of killing carnivores will depend on their behaviour, social organization, reproduction and dispersal patterns. We predicted that hunted jackals will alter demographic and reproductive patterns to compensate for increased mortality. Here, we collected demographic and reproductive information from harvested jackals and compared it between continually hunted (farms) and unmanaged populations (reserves). 3. The removal of jackals from farms results in a decrease in median age from 5–6 years (reserves) to 2–3 years (farms). Hunting also changed the age structure of jackal populations from a stable population to an expanding population. This may be ascribed to the compensatory immigration of individuals from neighbouring unmanaged areas, suggesting the formation of a source–sink system. Unmanaged areas may act as source populations exporting young, dispersing individuals to hunted areas which may act as sinks. This is likely driven by disruptions in the normal, mutually exclusive territorial system resulting in low densities of conspecifics on farms. 4. The low density of conspecifics allows younger individuals that would be socially precluded from reproducing to reproduce. Jackals on farms compensated for increased mortality by increasing the pregnancy rate of young individuals and increasing the litter size at younger ages, thereby increasing reproductive output. 5. Synthesis and applications. The lethal management of predators is the prevailing strategy to reduce livestock predation. However, the highly adaptable nature of jackals and the combination of compensatory mechanisms such as increased reproduction and potential for immigration allow these predators to persist in the face of severe anthropogenic mortality, possibly through the formation of a source–sink system. These compensatory processes will continue to counter population management actions as long as recruitment from unmanaged areas persists.

Megafaunal effects on vegetation structure throughout a densely wooded African landscape

Megafauna strongly affect vegetation structure and composition, often leading to management concern. However, the extent of their influence across large scales and varying ecosystems remains largely unknown. Using high resolution airborne Light Detection and Ranging (LiDAR), we investigated landscape-scale changes in vegetation height and three-dimensional (3D) structure across landscapes of varying elephant densities and presence over time, and in response to surface water distribution and terrain variability in the heavily managed thicket biome of the Addo Elephant National Park, South Africa. Elephants caused up to a fourfold reduction in vegetation height and altered the vertical profile, but increased vegetation height variability. Vegetation height also increased with elevation and distance from water, particularly in areas that elephants had long occupied at high densities. Slope had opposing effects on vegetation height, with height increasing with slope in areas long exposed to elephants, but decreasing where elephants had only recently been granted access. Our results suggest that elephants are the primary agents of vegetation change in this ecosystem, but that the strength of their effects varies across the landscape, enabling management to use water and terrain as mitigation tools. We further highlight the necessity of landscape-level experimental studies on megafaunal effects to untangle mechanisms and establish causality.

Brown hyena habitat selection varies among sites in a semi-arid region of southern Africa

Human/carnivore conflicts are common across the globe, and with a growing human population, this conflict is likely to increase as the space available to large carnivores is reduced. In South Africa, many small (< 400 km2), fenced protected areas have reintroduced persecuted carnivores, such as brown hyenas (Hyaena brunnea). These reserves have great potential to conserve brown hyena populations; consequently, understanding the limitations that small, fenced reserves impose on space use patterns is needed. We investigated the home range (95% fixed kernel utilization distributions) and landscape determinants of habitat selection using resource selection functions for 10 brown hyenas in 3 separate fenced reserves. Home range sizes were consistently smaller in 2 of the reserves when compared to the third. Considerable variation in the selection of habitat features exists among individual brown hyenas and reserves. The most important landscape determinant driving brown hyena space use was distance to roads, with brown hyenas observed closer to roads when compared to random locations within their ranges. If this relationship with roads holds outside of protected areas, it could represent a considerable threat to the species. Thus, obtaining a better understanding of the influence of roads on brown hyenas represents an important focus for future research.