The feral cat (Felis catus) is a key threat for many Australian native critical weight range animals (i.e. species of intermediate body mass between 35 and 5,500 g that are particularly susceptible to introduced predators) and estimates of cat abundance are required for assessing changes in population size. Camera trapping is a much used tool for monitoring and estimating population sizes, including with mark–resight techniques, for which the more robust estimators require individual identification. Many feral cats are individually marked, which potentially makes them suitable for such monitoring programmes. We sought to determine what proportion of cat images captured during a commonly used field deployment of camera traps could be individually identified, and whether aspects of camera trap deployment affected the rate of individual identification. Camera trap arrays were established in four conservation areas in south-west New South Wales, Australia, during 2017 (range 39–50 camera traps per site). The unlured camera traps were continuously deployed over 26 months, with five or 10 images captured per trigger. Where possible, cats were individually identified based on phenotypic characteristics. Over the deployment period (95,413 camera trap nights; CTN), we obtained 2.25 million images, of which 13,845 contained feral cats. Feral cat events (i.e. a series of images taken <5 minutes apart on the same camera trap) ranged from 0.004 to 0.047 events per CTN across the four conservation areas, with 85 individual cats identified. Depending on camera settings, few images could be assigned to a known individual (12.2–27.4% of feral cat events per site were of identifiable individuals). Minimum number known alive were 10–46 feral cats per site, with resultant quarterly densities ranging from 0.01 to 0.16 cats/km². With our current deployment, individual identification of feral cats was insufficient for estimating abundance or survival using individual mark–resight methods. Such deployment deficits limit the ecological conclusions that can be drawn from ours and similar studies.

中文翻译：

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从相机陷阱图像中可以单独识别出多少只野猫？人口监测、生态效用和相机陷阱设置

野猫 ( Felis catus) 是许多澳大利亚本土临界体重范围动物（即体重在 35 至 5,500 克之间的物种，特别容易受到引入的捕食者的影响）的主要威胁，并且需要估计猫的数量来评估种群规模的变化。相机诱捕是用于监测和估计种群规模的常用工具，包括使用标记重新瞄准技术，为此，更强大的估计器需要个体识别。许多野猫都有单独的标记，这可能使它们适合此类监测计划。我们试图确定可以单独识别在常用的现场部署相机陷阱期间捕获的猫图像的比例，以及相机陷阱部署的各个方面是否影响个体识别率。2017 年在澳大利亚新南威尔士州西南部的四个保护区建立了相机陷阱阵列（每个站点 39-50 个相机陷阱）。未引诱的相机陷阱在 26 个月内持续部署，每次触发捕获 5 或 10 张图像。在可能的情况下，根据表型特征对猫进行单独识别。在部署期间（95,413 个相机陷阱之夜；CTN），我们获得了 225 万张图像，其中 13,845 张包含野猫。野猫事件（即在同一相机陷阱上拍摄的一系列图像相隔 <5 分钟）在四个保护区的每个 CTN 发生 0.004 到 0.047 个事件，确定了 85 只个体猫。根据相机设置，很少有图像可以分配给已知个体（每个站点 12.2-27.4% 的野猫事件是可识别的个体）。² . 在我们目前的部署中，野猫的个体识别不足以使用个体标记重新观察方法估计数量或存活率。这种部署缺陷限制了可以从我们的研究和类似研究中得出的生态结论。