Abstract

Intense trapping of the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) for the international pet trade has devastated its populations across Indonesia such that populations of >100 individuals remain at only a handful of sites. We combined distance sampling with density surface modeling (DSM) to predict local densities and estimate total population size for one of these areas, Komodo Island, part of Komodo National Park (KNP) in Indonesia. We modeled local density based on topography (topographic wetness index) and habitat types (percentage of palm savanna and deciduous monsoon forest). Our population estimate of 1,113 (95% CI: 587–2,109) individuals on Komodo Island was considerably larger than previous conservative estimates. Our density surface maps showed cockatoos to be absent over much of the island, but present at high densities in wooded valleys. Coincidence between our DSM and a set of independent cockatoo observations was high (93%). Standardized annual counts by KNP staff in selected areas of the island showed increases in cockatoo records from <400 in 2011 to ~650 in 2017. Taken together, our results indicate that KNP, alongside and indeed because of preserving its iconic Komodo dragons (Varanus komodoensis), is succeeding in protecting a significant population of Indonesia’s rarest cockatoo species. To our knowledge this is the first time DSM has been applied to a critically endangered species. Our findings highlight the potential of DSM for locating abundance hotspots, identifying habitat associations, and estimating global population size in a range of threatened taxa, especially if independent datasets can be used to validate model predictions.

中文翻译：

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受龙的保护：密度表面建模证实了科莫多岛上大量濒临灭绝的黄冠凤头鹦鹉

摘要

强烈捕捞濒临灭绝的黄冠鹦鹉（Cacatua sulfurea），因为国际宠物贸易摧毁了整个印度尼西亚的人口，因此只有100个以上的地方居住着超过100个人的种群。我们将距离采样与密度表面建模（DSM）相结合，以预测局部密度，并估计这些区域之一的科莫多岛（印度尼西亚科莫多国家公园（KNP）的一部分）的总人口规模。我们基于地形（地形湿度指数）和栖息地类型（热带稀树草原和落叶季风森林的百分比）对局部密度进行建模。我们对科莫多岛的1,113个人（95％CI：587-2,109）的人口估计比以前的保守估计要大得多。我们的密度表面图显示，岛上大部分地区都没有鹦鹉，但是在树木繁茂的山谷中却以高密度出现。DSM与一组独立的美冠鹦鹉观测值之间的符合率很高（93％）。KNP在岛上某些地区的工作人员进行的标准化年度计数显示，鹦鹉的记录从2011年的<400增至2017年的650左右。总的来说，我们的结果表明，KNP与保存其标志性的科莫多巨蜥并存，实际上是因为Varanus komodoensis）已成功地保护了印度尼西亚最稀有的凤头鹦鹉物种的大量种群。据我们所知，这是帝斯曼首次将其用于濒危物种。我们的发现强调了帝斯曼（DSM）定位富集热点，识别栖息地协会以及估算一系列受威胁的类群的全球人口规模的潜力，特别是如果可以使用独立的数据集来验证模型预测的话。