In the California Current off the United States West Coast, there are three offshore cetacean species that produce narrow-band high frequency (NBHF) echolocation pulses: Dall's porpoise (Phocoenoides dalli) and two species of Kogia. NBHF pulses exist in a highly specialized acoustic niche thought to be outside the hearing range of killer whales and other potential mammal-eating odontocetes. Very little is known about the dwarf and pygmy sperm whales (K. sima and K. breviceps), including their NBHF pulse characteristics. This paper presents a multivariate clustering method using data from unmanned drifting acoustic recorders and visually verified porpoise recordings to discriminate between probable porpoise and Kogia clicks. Using density clustering, this study finds three distinct clusters whose geographic distributions are consistent with the known habitat range for Kogia and Dall's porpoise. A Random Forest classification model correctly assigned 97% of the clicks to their cluster. Visually verified Dall's porpoise clicks from towed hydrophones were strongly associated with one of the clusters, while a second cluster tended to be outside the geographic range of Dall's porpoise and unlike the Dall's porpoise cluster. These clicks, presumed to be made by Kogia, exhibited greater spectral variance than previous Kogia echolocation studies. It is possible that the structure of Kogia NBHF pulses may not be as stereotypical as previously described.

中文翻译：

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漂移记录仪对窄带高频回声定位咔嗒声的检测和分类。

在美国西海岸外的加利福尼亚洋流中，有三种近海鲸类物种产生窄带高频（NBHF）回声定位脉冲：达尔海豚（Phocoenoides dalli）和两种科贾物种。NBHF脉冲存在于高度专业化的声学环境中，被认为在虎鲸和其他潜在的食哺乳动物的齿状突科动物的听力范围之外。对矮鲸和侏儒抹香鲸（K. sima和K. breviceps）了解甚少，包括它们的NBHF脉冲特征。本文提出了一种多变量聚类方法，使用无人漂移声学记录仪的数据和目视验证的海豚记录来区分可能的海豚和科贾点击。使用密度聚类，这项研究发现了三个不同的聚类，它们的地理分布与Kogia和Dall的海豚的已知栖息地范围一致。随机森林分类模型正确地将97％的点击分配给了它们的群集。视觉验证的拖曳水听器发出的Dall的海豚咔嗒声与其中一个类密切相关，而第二个类则倾向于在Dall的海豚地理范围之外，与Dall的海豚类不同。这些点击（推测是由Kogia造成的）显示出比以前的Kogia回声定位研究更大的光谱方差。Kogia NBHF脉冲的结构可能不像前面描述的那样刻板。