Wittemyer George, Northrup Joseph M, Blanc Julian, Douglas-Hamilton Iain, Omondi Patrick, Burnham Kenneth P
Department of Fish, Wildlife, and Conservation Biology and Save the Elephants, Nairobi, Kenya 00200; Graduate Degree Program in Ecology, Colorado State University, Ft. Collins, CO 80523-1474;
Department of Fish, Wildlife, and Conservation Biology and.
Proc Natl Acad Sci U S A. 2014 Sep 9;111(36):13117-21. doi: 10.1073/pnas.1403984111. Epub 2014 Aug 18.
Illegal wildlife trade has reached alarming levels globally, extirpating populations of commercially valuable species. As a driver of biodiversity loss, quantifying illegal harvest is essential for conservation and sociopolitical affairs but notoriously difficult. Here we combine field-based carcass monitoring with fine-scale demographic data from an intensively studied wild African elephant population in Samburu, Kenya, to partition mortality into natural and illegal causes. We then expand our analytical framework to model illegal killing rates and population trends of elephants at regional and continental scales using carcass data collected by a Convention on International Trade in Endangered Species program. At the intensively monitored site, illegal killing increased markedly after 2008 and was correlated strongly with the local black market ivory price and increased seizures of ivory destined for China. More broadly, results from application to continental data indicated illegal killing levels were unsustainable for the species between 2010 and 2012, peaking to ∼ 8% in 2011 which extrapolates to ∼ 40,000 elephants illegally killed and a probable species reduction of ∼ 3% that year. Preliminary data from 2013 indicate overharvesting continued. In contrast to the rest of Africa, our analysis corroborates that Central African forest elephants experienced decline throughout the last decade. These results provide the most comprehensive assessment of illegal ivory harvest to date and confirm that current ivory consumption is not sustainable. Further, our approach provides a powerful basis to determine cryptic mortality and gain understanding of the demography of at-risk species.
非法野生动物贸易在全球范围内已达到惊人的程度，致使具有商业价值的物种数量锐减。作为生物多样性丧失的一个驱动因素，量化非法捕猎对于保护工作和社会政治事务至关重要，但却极其困难。在此，我们将基于实地的尸体监测与来自肯尼亚桑布鲁一个经过深入研究的野生非洲象种群的精细人口统计数据相结合，将死亡率划分为自然原因和非法原因。然后，我们扩展分析框架，利用濒危野生动植物种国际贸易公约项目收集的尸体数据，对区域和大陆尺度上大象的非法猎杀率及种群趋势进行建模。在受到密集监测的地点，2008年后非法猎杀显著增加，且与当地黑市象牙价格以及运往中国的象牙查获量的增加密切相关。更广泛地说，应用于大陆数据的结果表明，2010年至2012年期间，该物种的非法猎杀水平不可持续，2011年达到约8%的峰值，据此推断当年约有4万头大象被非法猎杀，该物种数量可能减少约3%。2013年的初步数据表明过度捕猎仍在继续。与非洲其他地区不同，我们的分析证实，中非森林象在过去十年中数量持续下降。这些结果提供了迄今为止对非法象牙捕猎最全面的评估，并证实当前的象牙消费是不可持续的。此外，我们的方法为确定隐秘死亡率和了解濒危物种的种群统计学提供了有力依据。
