Kissui Bernard M, Packer Craig
Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St Paul, MN 55108, USA.
Proc Biol Sci. 2004 Sep 7;271(1550):1867-74. doi: 10.1098/rspb.2004.2797.
Efforts to determine whether bottom-up or top-down processes regulate populations have been hampered by difficulties in accurately estimating the population's carrying capacity and in directly measuring food intake rate, the impacts of interspecific competition and exposure to natural enemies. We report on 40 years of data on the lion population in Ngorongoro Crater, Tanzania, which showed strong evidence of density-dependent regulation at 100-120 individuals but has remained below 60 individuals for the past decade despite consistently high prey abundance. The lions enjoy a higher per capita food-intake rate and higher cub recruitment at low population density, and interspecific competition has not increased in recent years. These animals have suffered from a number of severe disease outbreaks over the past 40 years, but, whereas the population recovered exponentially from a severe epizootic in 1963, three outbreaks between 1994 and 2001 have occurred in such rapid succession that the population has been unable to return to the carrying capacity. The Crater population may have become unusually vulnerable to infectious disease in recent years owing to its close proximity to a growing human population and a history of close inbreeding. The Crater lions may therefore provide important insights into the future of many endangered populations.
确定自下而上或自上而下的过程是否调控种群数量的努力，一直受到以下困难的阻碍：难以准确估计种群的承载能力，难以直接测量食物摄入率、种间竞争的影响以及天敌暴露情况。我们报告了坦桑尼亚恩戈罗恩戈罗火山口狮子种群40年的数据，这些数据显示，在种群数量为100 - 120只时存在密度依赖调控的有力证据，但在过去十年中，尽管猎物数量一直很高，种群数量仍一直低于60只。狮子在低密度种群时人均食物摄入率更高，幼崽存活率也更高，并且近年来种间竞争并未加剧。在过去40年里，这些动物遭受了多次严重疾病爆发，但1963年严重 epizootic 后种群呈指数级恢复，而1994年至2001年间的三次疫情爆发接连发生得如此迅速，以至于种群数量一直无法恢复到承载能力。由于与不断增长的人类种群距离很近且有近亲繁殖的历史，近年来火山口的狮子种群可能变得异常容易感染疾病。因此，火山口的狮子可能为许多濒危种群的未来提供重要见解。
