Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC, USA.
School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
J Anim Ecol. 2020 Feb;89(2):449-459. doi: 10.1111/1365-2656.13099. Epub 2019 Oct 4.
Research on drivers of demographic rates has mostly focused on top predators and their prey, and comparatively less research has considered the drivers of mesopredator demography. Of those limited studies, most focused on top-down effects of apex predators on mesopredator population dynamics, whereas studies investigating alternative mechanisms are less common. In this study, we tested hypotheses related to top-down, bottom-up and density-dependent regulation of demographic rates in an imperilled mesopredator, the cheetah (Acinonyx jubatus). We used a 25-year dataset of lion density, cheetah density and prey density from the Mun-Ya-Wana Conservancy in South Africa and assessed the effects of top-down, bottom-up and density-dependent drivers on cheetah survival and reproduction. In contrast to the top-down and bottom-up predictions, both adult and juvenile cheetahs experienced the lowest survival during months with high prey densities and low lion densities. We observed support only for a density-dependent response in juvenile cheetahs, where they had a higher probability of reaching independence during times with low cheetah density and low prey density. We did not identify any strong drivers of litter size. Collectively, our results indicate that high apex predator abundance might not always have negative effects on mesopredator populations, and suggest that context dependency in top-down, bottom-up and density-dependent factors may regulate demographic rates of cheetahs and other mesopredators. Our results highlight the complexities of population-level drivers of cheetah demographic rates and the importance of considering multiple hypotheses of mesopredator population regulation.
人口率驱动因素的研究主要集中在顶级捕食者及其猎物上，而相对较少的研究考虑了中型捕食者的种群动态的驱动因素。在那些有限的研究中，大多数集中在顶级掠食者对中型捕食者种群动态的自上而下的影响上，而研究替代机制的研究则较少。在这项研究中，我们检验了与自上而下、自下而上和密度依赖的人口率调节相关的假设，这些假设涉及处于濒危状态的中型捕食者——猎豹（Acinonyx jubatus）。我们使用了南非 Mun-Ya-Wana 保护区的 25 年狮子密度、猎豹密度和猎物密度数据集，并评估了自上而下、自下而上和密度依赖的驱动因素对猎豹的生存和繁殖的影响。与自上而下和自下而上的预测相反，成年和幼年猎豹在猎物密度高而狮子密度低的月份的存活率最低。我们只观察到了对幼年猎豹的密度依赖反应的支持，它们在猎豹密度和猎物密度低的时期达到独立的可能性更高。我们没有发现任何影响幼崽数量的强烈因素。总的来说，我们的结果表明，高顶级捕食者的数量并不总是对中型捕食者种群产生负面影响，并表明自上而下、自下而上和密度依赖因素的背景依赖性可能调节猎豹和其他中型捕食者的种群动态。我们的结果突出了影响猎豹种群动态的人口率驱动因素的复杂性，以及考虑多种中型捕食者种群调节假说的重要性。
