If there’s one thing people use to document a safari experience, it’s photographs. People can come back with dozens or even hundreds. Some of the snapshots might be a blurry image of a cheetah on the horizon. But others can capture the experience of an encounter and underlie our memories of it. For example, I’ll never forget the morning I photographed a hyena in Kruger National Park with the face of a lion cub in her mouth.
It’s not just tourists taking pictures of wildlife – it’s a commonly used tool for scientists and conservation professionals, who often undertake photographic surveys to understand the population dynamics of wildlife, individually identify animals, or assess species distributions.
What my colleagues Dr Caitlin Black (then my Postdoctoral Research Assistant at Cambridge University) and Dr Michelle Henley (Director of the non-profit Elephants Alive) and I wanted to do was to see whether we could pull even more data than originally intended out of survey photographs of elephants. Perhaps the distance between the observer and subject wasn’t known, but could we use ratios in terms of pixels on a photograph rather than cm on a tape measure to give us data? We were looking specifically at tusk size, age and whether males were in a state called, “musth” when they are exposed to high levels of male hormones, which affects their body and behavior.
我们有一个很棒的资源来测试这些想法：Michelle和她的团队正式在相关的私人自然保护区中正式调查大象，自2003年以来，与南非的克鲁格国家公园相邻。雄性大象。其中，我们能够分析406个男性的2,013张图像。
We compared ratios between body measurements extracted from the survey photographs to those taken the old-fashioned way with a tape measure when those same elephants had been darted and anesthetized so they could be fitted with satellite tracking collars. We recommend the use of two ratios in particular: tusk length to tusk diameter and tusk length to body height. The tusk length to body height ratio proved to be valid compared to ratios calculated from field measurements of the darted elephants, so can be used to compare tusk size between individual elephants. Likewise, the tusk length to tusk diameter ratio was also a valid method to estimate the age of elephants.
To determine musth status or sexual state, we used the visual signs of musth from the photos, including urine dribbling and splashes of urine on the back of legs, and secretion from temporal glands. These matched well with observer reports of whether or not the elephants were in musth.
Overall, our study shows that age, sexual state, and relative body measurements can be accurately and non-invasively measured by extracting the data from survey photos. Moreover, the photo database, originally created to identify individuals, provided morphometric information from over 40% of individual elephants. Although this method does not provide information on traditional morphometric measurements (e.g. tusk length in cm), it does let us use relative tusk size to compare individuals.
我们的方法有可能为生态学家，预备役经理和其他保护研究人员提供一种工具，以客观地识别男性大象的年龄和相对大小。由于将大量动物飞镖昂贵且潜在的风险，因此该方法可能很有用并应用于其他数据集或其他物种。
因此，下次您拍摄野生动植物的快照时，请记住，您可能不仅捕获了记忆，还可能正在查看一些重要的数据。
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