Bottlenose dolphin signature whistles are characterized by distinctive frequency modulation over time. The stable frequency contours of these whistles broadcast individual identity information. Little is known however, about whether or not the amplitude contour is also stereotyped. Here, we examined the relative amplitude-time contour of signature whistle emissions from eight bottlenose dolphins (Tursiops truncatus) in the U.S. Navy Marine Mammal Program (MMP) in San Diego, CA. The results suggested that unlike the stable frequency-time contour, the amplitude-time contour of signature whistles were largely non-stereotyped, characterized by large variability across multiple whistle emissions. Relative amplitude was negatively related to log peak frequency, with more energy focused in the lower frequency bands. This trend was consistent over all eight dolphins despite having quite different signature whistle contours. This relationship led to the amplitude contours being slightly more stereotyped within than between dolphins. We propose that amplitude across signature whistle emissions may serve as an avenue for encoding additional communicative information. We encourage future studies to incorporate analyses of amplitude contours in addition to frequency contours of signature whistles in order to begin to understand what role it may play in the dolphin communication system.

宽吻海豚标志性口哨的特点是随着时间的推移具有独特的频率调制。这些哨声的稳定频率等高线广播个人身份信息。然而，关于振幅轮廓是否也是刻板的，我们知之甚少。在这里，我们检查了八只宽吻海豚（Tursiops truncatus) 在加利福尼亚州圣地亚哥的美国海军海洋哺乳动物计划 (MMP) 中。结果表明，与稳定的频率 - 时间轮廓不同，签名哨子的幅度 - 时间轮廓在很大程度上是非定型的，其特征是多个哨子发射的变化很大。相对幅度与对数峰值频率呈负相关，更多的能量集中在较低的频段。尽管具有完全不同的标志性口哨轮廓，但所有八只海豚的这一趋势都是一致的。这种关系导致振幅等高线在海豚之间比在海豚之间更加刻板。我们建议签名哨子发射的幅度可以作为编码额外通信信息的途径。