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Accounting for animal density gradients using independent information in distance sampling surveys

机译：在距离抽样调查中使用独立信息来计算动物密度梯度

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摘要

Distance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue.
机译：距离采样被广泛用于估计动物的密度或丰度。传统方法假定线或点样线的位置相对于动物种群而言是随机的，但样线通常沿线性特征放置，例如道路，河流或海岸线，它们不会对研究区域进行随机采样，从而导致对丰度的估计存在偏差。如果有可能收集更多的数据来模拟相对于样线的动物密度梯度，我们将展示如何扩展传统的距离采样可能性，以给出覆盖区域密度的渐近无偏估计。我们通过使用沿轨道铺设的线样线调查的袋鼠数据，说明了所提出的方法，从独立来源获知了其真实密度，并且相对于轨道的密度梯度是从GPS圈养动物的样本中估算的。对于此示例，动物的密度随与轨道的距离增加而增加，因此，如果忽略样带的非随机位置，则检测概率被高估，而密度被低估。当我们考虑密度梯度时，在丰度估算中没有偏差的证据。最后，我们向进行距离采样调查的研究人员提出了一些实用建议，这些调查可能会影响密度梯度。

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  • 来源
    《Statistical Methods and Applications》 |2013年第1期|67-80|共14页
  • 作者

    Tiago A. Marques; Stephen T. Buckland; Regina Bispo; Brett Howland;

  • 作者单位

    Centre for Research into Ecological and Environmental Modelling, University of St Andrews,St Andrews, UK Centro de Estatistica e Aplicacoes da Universidade de Lisboa,Lisboa, Portugal;

    Centre for Research into Ecological and Environmental Modelling, University of St Andrews,St Andrews, UK;

    ISPA, Instituto Universitario, Lisbon, Portugal R. Bispo,Bio3 - Estudos e Projectos em Biologia e Valorizacao de Recursos Naturais,Lda, Portugal;

    Fenner School of Environment and Society, ANU College of Medicine, Biology & Environment, The Australian National University, Canberra, Australia;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    density gradients; distance sampling; kangaroo; road surveys; line and point transects; wildlife abundance;

    机译：密度梯度;距离采样;袋鼠;道路调查;线和点样条线;野生动植物丰富;

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