Blue whale migratory traditions

Researchers have observed that Pacific blue whales return to the same places every year and on similar dates. Curiously, their feeding grounds are not necessarily the most productive areas. Rather, they are the most predictable ones. By favouring stability over quantity, blue whales avoid unpleasant surprises in a highly variable ecosystem. Blue whales are able to benefit from this strategy because they have a life expectancy of 80 years, which allows for long-term learning.

This new knowledge on blue whale migration will provide a better understanding as to how climate change is likely to affect this endangered species. Marine mammals are particularly vulnerable to rapid change because they are infrequent breeders. Natural selection, which allows animals to adapt to new environmental conditions, takes place at the same rate as reproduction. Animals that produce multiple offspring every year, such as rodents, can adapt much more quickly than those that reproduce more slowly. Additionally, if blue whale mortality were to spike due to a lack of food, the birth rate would not be able to immediately compensate.

If krill were to suddenly move north due to rising water temperatures, the consistency of the blue whale’s migration pattern could be detrimental. A number of bad years may be needed to affect the overall good productivity that is burned into the blue whales’ memory. Furthermore, unlike humpbacks, which feed on krill and small fish, blue whales are specialists: they eat exclusively krill. Adaptability is therefore not the blue whale’s strong suit.

There remains much to learn about the migration of blue whales. For example, we do not know which migratory mechanisms are employed by the youngest whales, which have migrated only a few times. Do they follow their elders or do they go their own way?