Department of Biology, Syracuse University, 114 Life Sciences Complex, Syracuse, NY 13244, USA.
NOAA Fisheries, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543, USA.
Biol Lett. 2019 Oct 31;15(10):20190485. doi: 10.1098/rsbl.2019.0485. Epub 2019 Oct 9.
Mammals with dependent young often rely on cryptic behaviour to avoid detection by potential predators. In the mysticetes, large baleen whales, young calves are known to be vulnerable to direct predation from both shark and orca predators; therefore, it is possible that mother-calf pairs may show cryptic behaviours to avoid the attention of predators. Baleen whales primarily communicate through low-frequency acoustic signals, which can travel over long ranges. In this study, we explore the potential for acoustic crypsis, a form of cryptic behaviour to avoid predator detection, in North Atlantic right whale mother-calf pairs. We predicted that mother-calf pairs would either show reduced calling rates, reduced call amplitude or a combination of these behavioural modifications when compared with other demographic groups in the same habitat. Our results show that right whale mother-calf pairs have a strong shift in repertoire usage, significantly reducing the number of higher amplitude, long-distance communication signals they produced when compared with juvenile and pregnant whales in the same habitat. These observations show that right whale mother-calf pairs rely upon acoustic crypsis, potentially to minimize the risk of acoustic eavesdropping by predators.
依赖幼崽的哺乳动物通常依赖于隐藏行为来避免潜在捕食者的发现。在须鲸目中，大型须鲸的幼崽已知容易受到鲨鱼和逆戟鲸捕食者的直接捕食；因此，母子对可能会表现出隐藏行为来避免被捕食者注意。须鲸主要通过低频声信号进行交流，这些信号可以传播很远的距离。在这项研究中，我们探索了北大西洋露脊鲸母子对可能采用的声学伪装行为，以避免被捕食者发现。我们预测，与同一栖息地的其他群体相比，母子对的叫声频率、叫声幅度或这些行为改变的组合会减少。我们的结果表明，露脊鲸母子对的曲目使用有了明显的转变，与同一栖息地的幼年和怀孕的鲸鱼相比，它们发出的高振幅、长距离通讯信号数量显著减少。这些观察结果表明，露脊鲸母子对依赖声学伪装，可能是为了最大限度地降低被捕食者声学监听的风险。
