Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Long Marine Laboratory, 130 McAllister Way, Santa Cruz, CA 95060, USA
Institute of Marine Sciences, University of California Santa Cruz, Long Marine Laboratory, 115 McAllister Way, Santa Cruz, CA 95060, USA.
Proc Biol Sci. 2018 Nov 28;285(1892):20182176. doi: 10.1098/rspb.2018.2176.
Vocal dialects are fundamental to our understanding of the transmission of social behaviours between individuals and populations, however few accounts trace this phenomenon among mammals over time. Northern elephant seals () provide a rare opportunity to examine the trajectory of dialects in a long-lived mammalian species. Dialects were first documented in the temporal patterns of the stereotyped vocal displays produced by breeding males at four sites in the North Pacific in 1968 and 1969, as the population recovered from extreme exploitation. We evaluated the longevity of these geographical differences by comparing these early recordings to calls recently recorded at these same locations. While the presence of vocal dialects in the original recordings was re-confirmed, geographical differences in vocal behaviour were not found at these breeding rookeries nearly 50 years later. Moreover, the calls of contemporary males displayed more structural complexity after approximately four generations, with substantial between-individual variation and call features not present in the historical data. In the absence of measurable genetic variation in this species-owing to an extreme population bottleneck-a combination of migration patterns and cultural mutation are proposed as factors influencing the fall of dialects and the dramatic increase in call diversity.
声乐曲调对于我们理解个体和群体之间社会行为的传播至关重要，但很少有研究能长期追踪哺乳动物中的这种现象。北方象海豹（Northern elephant seals）为我们提供了一个难得的机会，可以研究长寿哺乳动物物种中声乐曲调的变化轨迹。1968 年和 1969 年，在北太平洋的四个地点，繁殖雄性海豹发出的刻板的发声表现出有规律的时间模式，声乐曲调首次被记录下来，当时该种群正从极度开发中恢复。我们通过将这些早期的录音与在这些相同地点最近录制的录音进行比较，评估了这些地理差异的持久性。虽然在原始录音中再次确认了存在声乐曲调，但在将近 50 年后的这些繁殖栖息地中，没有发现声音行为存在地理差异。此外，与历史数据相比，当代雄性海豹的叫声在大约四代之后显示出更高的结构复杂性，具有个体间的大量差异以及特征不同的叫声。由于该物种经历了极端的种群瓶颈，没有可测量的遗传变异，因此人们提出了迁移模式和文化突变的组合，作为影响声乐曲调下降和叫声多样性急剧增加的因素。
