McKnight Donald T, Ligon Day B
Department of Biology, Missouri State University, Springfield, Missouri, United States of America.
PLoS One. 2017 Aug 29;12(8):e0184101. doi: 10.1371/journal.pone.0184101. eCollection 2017.
Wildlife populations often exhibit unequal catchability between subgroups such as males and females. This heterogeneity of capture probabilities can bias both population size and sex ratio estimates. Several authors have suggested that this problem can be overcome by treating males and females as separate populations and calculating a population estimate for each of them. However, this suggestion has received little testing, and many researchers do not implement it. Therefore, we used two simulations to test the utility of this method. One simulated a closed population, while the other simulated an open population and used the robust design to calculate population sizes. We tested both simulations with multiple levels of heterogeneity, and we used a third simulation to test several methods for detecting heterogeneity of capture probabilities. We found that treating males and females as separate populations produced more accurate population and sex ratio estimates. The benefits of this method were particularly pronounced for sex ratio estimates. When males and females were included as a single population, the sex ratio estimates became inaccurate when even slight heterogeneity was present, but when males and females were treated separately, the estimates were accurate even when large biases were present. Nevertheless, treating males and females separately reduced precision, and this method may not be appropriate when capture and recapture rates are low. None of the methods for detecting heterogeneity were robust, and we do not recommend that researchers rely on them. Rather, we suggest separating populations by sex, age, or other subgroups whenever sample sizes permit.
野生动物种群中，不同亚组（如雄性和雌性）的可捕获性往往存在差异。捕获概率的这种异质性可能会使种群规模和性别比估计产生偏差。一些作者建议，将雄性和雌性视为独立种群，并分别计算每个种群的估计值，以此来克服这一问题。然而，这一建议几乎未得到验证，许多研究人员也未采用。因此，我们通过两个模拟试验来检验该方法的实用性。一个模拟封闭种群，另一个模拟开放种群，并使用稳健设计来计算种群规模。我们在多个异质性水平下对两个模拟试验进行了测试，并用第三个模拟试验来检验几种检测捕获概率异质性的方法。我们发现，将雄性和雌性视为独立种群能得出更准确的种群规模和性别比估计值。该方法在性别比估计方面的优势尤为明显。当将雄性和雌性作为一个单一种群时，即使存在轻微的异质性，性别比估计也会变得不准确，但当分别处理雄性和雌性时，即使存在较大偏差，估计值仍然准确。尽管如此，分别处理雄性和雌性会降低估计精度，当捕获和重捕率较低时，这种方法可能并不适用。检测异质性的方法都不可靠，我们不建议研究人员依赖这些方法。相反，我们建议只要样本量允许，就按性别、年龄或其他亚组对种群进行划分。
