Male biased sex ratio of poached elephants is negatively related to poaching intensity over time
Male biased sex ratio of poached elephants is negatively related to poaching intensity over time
复制标题
DOI：
10.1007/s10592-014-0603-2
复制
发表时间：
2014-10-01
影响因子：
2.2
通讯作者：
Wasser, Samuel K.
中科院分区：
文献类型：
--
作者：
Mondol, Samrat;Mailand, Celia R.;Wasser, Samuel K.
在过去的几十年里，偷猎和栖息地的丧失导致非洲象的数量和范围大幅下降，自2006年以来，象牙禁令后最大的损失发生了。偷猎的目标是体型最大的个体，因为它们的象牙更大。这也会使偷猎倾向于雄性。我们假设，在严重盗猎的种群中，大象的性别比例最初会强烈偏向雄性，但随着时间的推移，在严重盗猎的地区，雄性的偏向会逐渐减少。这种情况之所以会发生，是因为一旦最大的雄性被杀死，年老的雌性母象最终会提供下一个大型象牙的来源。在本文中，我们研究了2002年至2013年间缉获的大量象牙（0.5-6.5吨）中象牙样本的性别比例。这些大规模缉获的来源是独立确定的，在大多数情况下，包括在同一地点或附近地点偷猎的个人。我们的研究结果表明，在这些大型象牙缉获案中，存在男性比例偏倚的现象。最早和最大的查获（2002年查获6.5吨）来自赞比亚的男性比后来的查获多4-6倍。然而，随着时间的推移，来自同一个严重偷猎地区的样本中的男性偏见逐渐减少，这表明女性目标增加。鉴于母象对大象社会结构和人口增长的重要性，这些趋势可能会对大象的恢复产生负面影响。
Poaching and habitat loss has caused a massive decline in the number and range of African elephants over the past few decades, with the greatest post ivory ban losses occurring since 2006. Poaching targets the largest individuals for their greater tusk sizes. This should also bias poaching towards males. We hypothesized that elephant sex ratios from heavily poached populations will initially be strongly male biased, but become progressively less male biased in heavily poached areas over time. This will occur because large, older female matriarchs will eventually provide the next source of large tusks once the largest males are killed. In this paper, we examined the sex ratio of ivory samples from very large ivory seizures (0.5-6.5 tons) made between 2002 and 2013. Origins of these large seizures were independently determined and in most cases, consisted of individuals poached in the same or nearby location. Our results indicate a male-biased sex ratio among these large ivory seizures. The earliest and largest seizure (6.5 tons seized in 2002) from Zambia was 4-6 times more male biased than later seizures. However, male bias progressively declined in samples that originated from that same, heavily poached area over time, indicating a rise in female targets. These trends are likely to have negative implications on elephant recovery given the importance of female matriarchs to elephant social structure and population growth.