Reyes de Merkle Johnathan, Creel Scott, Becker Matthew S, Goodheart Ben, Mweetwa Thandiwe, Mwape Henry, Dröge Egil, Simpamba Twakundine
Zambian Carnivore Programme Mfuwe Eastern Province Zambia.
Department of Ecology Montana State University Bozeman Montana USA.
Ecol Evol. 2024 Jun 25;14(6):e11402. doi: 10.1002/ece3.11402. eCollection 2024 Jun.
Within carnivore guilds, dominant competitors (e.g., lions, ) are limited primarily by the density of prey, while subordinate competitors (e.g., African wild dogs, ) 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 km. 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.
在食肉动物群落中，优势竞争者（如狮子）主要受猎物密度的限制，而从属竞争者（如非洲野犬）则受优势竞争者密度的限制。从历史上看，从属竞争者的适应性和种群密度与猎物密度并没有紧密联系。然而，由于人类影响，撒哈拉以南非洲的大型食草动物数量大幅下降，在猎物枯竭严重的地方，竞争从属者的适应性成本可能开始超过竞争释放带来的好处。通过对赞比亚卢安瓜谷生态系统（LVE）中的非洲野犬进行长期密集监测，我们测试了猎物枯竭对生存和繁殖的影响。我们假设，尽管狮子密度较低，但在猎物枯竭的地区，非洲野犬的适应性会更低。我们的研究区域包括四个相邻地区，这些地区在保护水平、猎物密度和狮子密度方面各不相同。我们拟合了贝叶斯Cormack-Jolly-Seber模型和封闭捕获模型来估计对生存和种群密度的影响，并使用广义线性模型来估计对繁殖成功率的影响。我们发现，卢安瓜谷生态系统是非洲野犬的一个据点，估计中位密度为每100平方公里4.0只个体。尽管密度很高，但不同地区的生存和繁殖情况有所不同，在猎物密度最低的地区，适应性的两个组成部分都大幅下降。人为造成的猎物枯竭正成为非洲野犬的一个重要限制因素。如果猎物枯竭（或任何其他形式的栖息地退化）变得足够严重，以至于其适应性成本超过了竞争释放的好处，那么这种变化可能会从根本上改变竞争从属物种限制因素之间的平衡。
