Mote Marine Laboratory, Sarasota, FL, USA.
The Rockefeller University, New York, NY, USA.
Sci Rep. 2022 Nov 15;12(1):19597. doi: 10.1038/s41598-022-23321-7.
Vocal activity and signal characteristics of mammals are driven by several factors that result in both stability and plasticity over multiple time scales. All three extant species of manatee communicate with several calls that are especially important for maintaining contact between cows and calves. Determining if calf calls differ across manatee species will provide insights into the evolution of species-specific acoustic communication traits. We investigated the interspecific differences in the vocalizations of calves of Amazonian manatees (Trichechus inunguis) and the two subspecies of the West Indian manatee (T. manatus). Vocalizations of individual calves were recorded in rehabilitation centers in Brazil, Puerto Rico, the United States, and Mexico. The acoustic structure of calls produced by manatee calves varied between species and with body size. Amazonian manatee calves produced shorter calls with multiple notes at higher frequency while West Indian calves produced modulated calls that were lower in frequency and longer in duration. Smaller West Indian calves produced frequency modulated, hill-shaped calls that flattened with an increase in body length. Our results provide evidence for divergence in the ontogeny of vocalizations across T. manatus and T. inunguis and suggest variation in body size contributed to the evolution of differences in the characteristics of their calls.
哺乳动物的发声活动和信号特征受多种因素驱动，这些因素在多个时间尺度上导致了稳定性和可塑性。所有现存的三种海牛物种都通过几种叫声进行交流，这些叫声对于维持牛群和小牛之间的联系尤为重要。确定小牛的叫声是否在海牛物种之间存在差异，将有助于深入了解物种特异性声音交流特征的进化。我们研究了亚马逊海牛（Trichechus inunguis）和西印度海牛（T. manatus）两个亚种的小牛在发声方面的种间差异。在巴西、波多黎各、美国和墨西哥的康复中心记录了个别小牛的发声。海牛小牛发出的叫声的声学结构在物种之间和体型之间存在差异。亚马逊海牛小牛发出的叫声较短，有多个音符，频率较高，而西印度小牛发出的叫声则频率较低，持续时间较长。体型较小的西印度小牛发出的是调频、山形的叫声，随着体长的增加而变平。我们的研究结果为 T. manatus 和 T. inunguis 的发声发育中的差异提供了证据，并表明体型的差异导致了它们叫声特征的进化差异。
