Whale geography: A species-centric approach applied to migration

摘要

Understanding the biogeography of a species begins by mapping its presence over time and space. The use of home ranges, breeding and feeding areas, migration paths and movement patterns between the two are also inherent to their ecology. However, this is an overly simplified view of life histories. It ignores nuanced and complex exchanges and responses to the environment and between conspecifics. Having previously advocated for a more species-centric approach in a discussion of 'whale geography', I look to better understand the driving factors of migrations, and the information streams guiding the movement, which is key to the biogeography of large whale species. First, I consider the processes underlying the navigation capacities of species to complete migration, and how, and over what scales, sensory information contributes to cognitive maps. I specifically draw on examples of large-scale, en masse migrators to then apply this to whales. I focus on the acoustic sense as the principal way whales gain and exchange information, drawing on a case study of grey whale (Eschrichtius robustus) calling behaviour to illustrate my arguments. Their consistent employment of far-propagating calls appears to be tied to travel behaviours and probably aids navigation and social cohesion. The range over which calls are being propagated to conspecifics, or perhaps being echoed back to the individual, underlies the distance over which the cognitive maps are being both formed and employed. I believe understanding these processes edges us closer to understanding species biogeography.