Data from: Compensatory life history responses of a mesopredator may undermine carnivore management efforts

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. 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). 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. 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. 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.旨在降低食肉动物危害的致死性食肉动物管控，是一种在全球范围内广泛实施却威胁诸多食肉动物种群存续的现象。黑背胡狼（Canis mesomelas）是南非地区引发牲畜捕食事件的主要元凶，为降低其对牲畜的危害，人类对其开展了广泛的猎杀活动。尽管已实施数百年的致死性管控，黑背胡狼种群依然得以存续。与胡狼类似的小型犬科动物具有极强的适应性，且对致死因素的响应存在显著差异，这可能会影响管控效果。对食肉动物进行猎杀所产生的效应，取决于其行为、社会组织、繁殖以及扩散模式。我们提出假说：受猎杀的胡狼种群会调整种群动态与繁殖模式，以弥补死亡率升高带来的损失。本研究从被猎杀的黑背胡狼个体中收集了种群动态与繁殖相关信息，并将其与持续受猎杀的种群（农场区域）以及未受管控的种群（保护区）进行对比。对农场区域内的胡狼进行移除后，种群的中位年龄从保护区的5~6岁降至农场的2~3岁。猎杀还使胡狼种群的年龄结构从稳定种群转变为扩张型种群。这一现象或许可归因于周边未受管控区域个体的补偿性迁入，提示源-汇系统（source–sink system）的形成。未受管控的区域可作为源种群，输出年轻的扩散个体至受猎杀的汇种群区域。这一过程可能源于原本相互排他的领地系统被打破，使得农场区域内同种个体的种群密度偏低。低密度的同种个体环境，使得原本会被社会机制抑制繁殖的年轻个体得以参与繁殖。农场区域的胡狼通过提高年轻个体的妊娠率，以及增加幼崽的窝仔数，来提升繁殖输出，以此弥补死亡率升高的损失。总结与应用：致死性食肉动物管控是当下降低牲畜捕食危害的主流策略。然而，黑背胡狼极强的适应性，加上繁殖能力提升、潜在迁入能力等补偿性机制的共同作用，使得这些食肉动物能够在严重的人为致死压力下持续存续，这一过程可能通过源-汇系统得以实现。只要未受管控区域仍有个体迁入，这些补偿过程就会持续抵消种群管控措施的效果。