Ginsberg J R, Mace G M, Albon S
Institute of Zoology, Zoological Society of London, U.K.
Proc Biol Sci. 1995 Nov 22;262(1364):221-8. doi: 10.1098/rspb.1995.0199.
Altered assumptions about how different ecological factors limit population numbers may lead to different conclusions about the causes of decline and ultimate extinction of a small population. Here, alternative hypotheses for the local disappearance of the Serengeti plains study population of African wild dogs (Lycaon pictus) are examined in light of observations of density dependence, deterministic decline and frequent rapid fluctuations in population number. After a population crash from 60 individuals in 1975 to 30 individuals in 1976, the Serengeti plains population fluctuated around a mean value of 22 individuals for 16 years before local extinction occurred. Variation in population numbers was extreme, with inter-annual reductions in population size of at least 40% occurring three times. Several explanations are consistent with the observed trends in population size including outbreaks of various epizootics and competition with other predators. Monte Carlo simulation, with parameters set to reflect observed fluctuations, demonstrate that population extinction was likely from chance factors alone. In small and declining populations, for which precise data and controls are unavailable, determining the cause(s) of extinction usually will be impossible.
关于不同生态因素如何限制种群数量的假设发生变化，可能会导致对小种群数量下降及最终灭绝原因得出不同结论。在此，根据对密度依赖性、确定性下降以及种群数量频繁快速波动的观察，对塞伦盖蒂平原非洲野犬（非洲野犬属）研究种群在当地消失的替代假说进行了研究。在种群数量从1975年的60只骤降至1976年的30只后，塞伦盖蒂平原的种群数量在当地灭绝前的16年里围绕22只的平均值波动。种群数量变化极大，种群规模至少40%的年度减少出现了三次。几种解释与观察到的种群数量趋势相符，包括各种动物流行病的爆发以及与其他捕食者的竞争。将参数设置为反映观察到的波动情况的蒙特卡洛模拟表明，仅偶然因素就可能导致种群灭绝。对于那些无法获得精确数据和控制措施的小且数量在减少的种群，通常不可能确定灭绝的原因。
