Institute of Natural and Mathematical Sciences, Massey University, Auckland, 0745, New Zealand.
National Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Wellington, 6021, New Zealand.
Sci Rep. 2018 Aug 22;8(1):12593. doi: 10.1038/s41598-018-30842-7.
Dolphin photo-identification has traditionally relied only on distinctive markings on the dorsal fin-this is problematic for delphinids whose populations exhibit a low mark ratio. We used common dolphins (genus Delphinus) as a model species to assess the viability of using pigmentation for photo-identification. Using a photo-identification catalogue of 169 adult individuals collected between 2002 and 2013, we extracted features that quantified pigmentation in a manner that was robust to lighting artefacts and dorsal fin orientation. We determined the proportion of individuals which exhibited pigmentation and examined temporal stability by (i) visually examining individuals and (ii) testing for seriation. We found 88-91% of images could be manually matched to the correct individual in the catalogue based on pigmentation patterns alone. A linear discriminant analysis classifier correctly identified the correct individual 77% of the time. We found 95% common dolphins exhibited distinctive pigmentation-all of which were temporarily stable. Our work challenges the current thinking that pigmentation is an unreliable feature for delphinid photo-identification and suggests that this feature could be applied to common dolphins and other poorly-marked delphinids.
海豚的照片识别传统上仅依赖于背鳍上的独特标记——对于标记比例低的海豚种群来说，这是有问题的。我们使用宽吻海豚（属 Delphinus）作为模型物种，评估使用色素进行照片识别的可行性。使用 2002 年至 2013 年间收集的 169 名成年个体的照片识别目录，我们提取了量化色素的特征，这些特征在光照伪影和背鳍方向方面具有稳健性。我们确定了表现出色素的个体比例，并通过（i）目视检查个体和（ii）测试序列化来检查时间稳定性。我们发现，仅根据色素模式，88-91%的图像可以手动与目录中的正确个体匹配。线性判别分析分类器正确识别正确个体的时间为 77%。我们发现 95%的宽吻海豚表现出独特的色素——所有这些色素都是暂时稳定的。我们的工作挑战了当前认为色素是海豚照片识别不可靠特征的观点，并表明该特征可应用于宽吻海豚和其他标记不明显的海豚。
