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一刀切的方法不适用:需要灵活的模型来理解跨尺度的动物运动。

One size does not fit all: flexible models are required to understand animal movement across scales.

机构信息

Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, NY 10027, USA.

出版信息

J Anim Ecol. 2011 Sep;80(5):1088-96. doi: 10.1111/j.1365-2656.2011.01851.x. Epub 2011 Apr 27.

Abstract
  1. Large data sets containing precise movement data from free-roaming animals are now becoming commonplace. One means of analysing individual movement data is through discrete, random walk-based models. 2. Random walk models are easily modified to incorporate common features of animal movement, and the ways that these modifications affect the scaling of net displacement are well studied. Recently, ecologists have begun to explore more complex statistical models with multiple latent states, each of which are characterized by a distribution of step lengths and have their own unimodal distribution of turning angles centred on one type of turn (e.g. reversals). 3. Here, we introduce the compound wrapped Cauchy distribution, which allows for multimodal distributions of turning angles within a single state. When used as a single state model, the parameters provide a straightforward summary of the relative contributions of different turn types. The compound wrapped Cauchy distribution can also be used to build multiple state models. 4. We hypothesize that a multiple state model with unimodal distributions of turning angles will best describe movement at finer resolutions, while a multiple state model using our multimodal distribution will better describe movement at intermediate temporal resolutions. At coarser temporal resolutions, a single state model using our multimodal distribution should be sufficient. We parameterize and compare the performance of these models at four different temporal resolutions (1, 4, 12 and 24 h) using data from eight individuals of Loxodonta cyclotis and find support for our hypotheses. 5. We assess the efficacy of the different models in extrapolating to coarser temporal resolution by comparing properties of data simulated from the different models to the properties of the observed data. At coarser resolutions, simulated data sets recreate many aspects of the observed data; however, only one of the models accurately predicts step length, and all models underestimate the frequency of reversals. 6. The single state model we introduce may be adequate to describe movement data at many resolutions and can be interpreted easily. Multiscalar analyses of movement such as the ones presented here are a useful means of identifying inconsistencies in our understanding of movement.
摘要
  1. 现在,包含自由漫游动物精确运动数据的大型数据集已变得越来越普遍。分析个体运动数据的一种方法是通过离散的、基于随机游走的模型。

  2. 随机游走模型很容易修改以纳入动物运动的常见特征,并且这些修改如何影响净位移缩放的方式已经得到了很好的研究。最近,生态学家开始探索具有多个潜在状态的更复杂的统计模型,每个潜在状态都由一系列步长分布和其自身的关于单一转弯类型(例如反转)的单峰转弯角度分布来描述。

  3. 在这里,我们引入了复合缠绕 Cauchy 分布,该分布允许在单个状态内存在多峰转弯角度分布。当用作单个状态模型时,参数提供了不同转弯类型的相对贡献的直接总结。复合缠绕 Cauchy 分布也可用于构建多状态模型。

  4. 我们假设,具有单峰转弯角度分布的多状态模型将最好地描述更精细分辨率下的运动,而使用我们的多峰分布的多状态模型将更好地描述中间时间分辨率下的运动。在更粗糙的时间分辨率下,使用我们的多峰分布的单个状态模型应该就足够了。我们在四个不同的时间分辨率(1、4、12 和 24 小时)下对这些模型进行参数化和性能比较,并使用来自 8 只 Loxodonta cyclotis 的个体的数据进行了验证。

  5. 我们通过将不同模型模拟的数据与观察数据的属性进行比较,评估了不同模型在向更粗糙的时间分辨率外推的有效性。在更粗糙的分辨率下,模拟数据集再现了观察数据的许多方面;然而,只有一个模型准确地预测了步长,并且所有模型都低估了反转的频率。

  6. 我们引入的单状态模型可能足以描述许多分辨率下的运动数据,并且易于解释。运动的多尺度分析,如这里提出的分析,是识别我们对运动理解的不一致性的有用方法。

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