Cruising the whale superhighway: The evolution, biomechanics, and ecological drivers of migration in cetaceans

Whales are a diverse group of aquatic mammals that fill a wide range of important roles within marine communities. One surprising behaviour they exhibit is the remarkable ability to travel huge distances across the world every year in their annual migrations. They migrate from polar regions, where food is plentiful, to regions nearer the tropics where they can raise their young away from predators. Long-distance migration in whales is ecologically important because they transfer huge quantities of nutrients from the food they eat at the poles, which they then release in breeding regions through defecation or by dying. For example, a fallen whale body on the seabed provides the basis for an entire marine ecosystem. While fully-aquatic whales evolved over 40 million years ago, it is unclear when in their long evolutionary history migration began. It has been hypothesized that global climatic change, such as formation of the polar ice caps may have provided the environmental impetus for whale migration, but the link between behaviour, ecology, and evolution is poorly understood. This research will investigate long-distance migration in modern whales, then apply this knowledge to understanding how and when migratory behaviours evolved in ancient whales. We aim to investigate both the functional changes in morphology that enable long-distance migration and the environmental factors that drove the onset of these epic journeys. First, we will investigate how whale body shape has adapted to facilitate long-distance swimming in modern whales. We will ask: are migratory whales biomechanically optimized for swimming long distances? We will do this by measuring body shape variation in whales, and using computer models to estimate the fluid dynamics of whale swimming. Next, we will examine the environmental drivers that underlie whale migration and predict when they arose in earth history. We will ask: How do the environmental conditions in whale breeding and feeding grounds differ? And, when do these particular environments appear in the geological record? To do this, we will combine data from whale sightings around the world with environmental data, and state-of-the-art reconstructions of oceanic conditions throughout the Cenozoic. Finally, we will reconstruct the evolutionary history of both anatomical adaptations and ecology associated with migration. We will ask: When in whale evolution do we see the combination of swimming adaptations and ecological niches that indicate migratory behaviour? To do this, we will compare morphological and ecological features broadly across the phylogenetic tree of whales, reconstructing the most likely evolutionary sequence of events. This project proposes a unique combination of approaches to address an important evolutionary question. This will not only provide new insights into whales, their ecology, evolution, and behaviour; it will shed light on the deep-time origins of a process which is key to oceanic ecosystem function, and provide a case-study for the combination of anatomical and ecological evidence in studies of extinct species. By better understanding the relationship between whale migration and environmental change through time, we lay the groundwork for understanding the impact of anthropogenic changes on the future conservation risks of these iconic ocean giants.