Ocean Associates, Inc., 4007 N Abingdon Street, Arlington, Virginia 22207, USA.
Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, 8901 La Jolla Shores Boulevard, La Jolla, California 92037, USA.
J Acoust Soc Am. 2020 May;147(5):3511. doi: 10.1121/10.0001229.
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.
在美国西海岸的加利福尼亚海流中，有三种近海鲸类物种会产生窄带高频（NBHF）回声定位脉冲：白腰鼠海豚（Phocoenoides dalli）和两种 Kogia 属物种。NBHF 脉冲存在于一个高度专业化的声学生态位，据认为其在逆戟鲸和其他潜在的食哺乳动物齿鲸的听觉范围之外。对于小抹香鲸和小侏儒抹香鲸（K. sima 和 K. breviceps），包括它们的 NBHF 脉冲特征，人们知之甚少。本文提出了一种使用无人漂流声学记录器和视觉验证的鼠海豚记录数据进行多元聚类的方法，以区分可能的鼠海豚和 Kogia 咔哒声。使用密度聚类，本研究发现了三个不同的聚类，其地理分布与已知的 Kogia 和白腰鼠海豚的栖息地范围一致。随机森林分类模型正确地将 97%的咔哒声分配到其聚类中。从拖曳式水听器中获取的视觉验证的白腰鼠海豚咔哒声与其中一个聚类强烈相关，而第二个聚类则倾向于不在白腰鼠海豚的地理范围内，与白腰鼠海豚聚类不同。这些咔哒声，据推测是由 Kogia 发出的，其频谱变化大于之前的 Kogia 回声定位研究。Kogia 的 NBHF 脉冲结构可能不像以前描述的那样刻板。
