William K. Oestreich, Briana Abrahms, Megan F. McKenna, Jeremy A. Goldbogen, Larry B. Crowder, and John P. Ryan
This is a plain language summary of a Functional Ecology research article. Read the research in full here.
Long-distance migration is among the most awe-inspiring biological spectacles on Earth, and is critical to the survival of many species. Many long-distance migrants move seasonally between habitats which are preferable for different behaviors (e.g., feeding, reproduction) during different times of year. But the exact timing of ideal conditions for a given behavior (e.g., availability of food) varies year-to-year, and in many cases is shifting in the long-term due to the impacts of climate change on seasonality. Are long-distance migrants able to time their migrations flexibly year-to-year to match variability and changes in the ecosystems they inhabit? And if so, what information do migratory animals use to decide when to feed and when to migrate? We know surprisingly little about the answers to these questions for most migratory species, especially in the oceans, where persistent observation of many individuals’ behavior is particularly challenging.
The endangered Eastern North Pacific blue whale population relies on intensive feeding on krill during summer and fall off the west coast of North America to fuel a several-thousand-kilometer round-trip migration to and from breeding grounds off the west coast of Central America. Given that these whales will feed very little (if at all) during the 6-7 months away from their feeding grounds, the decision of when to depart is critical to population health. By continuously listening to and analysing patterns of blue whale songs off California for six years, we found that blue whales’ transition from feeding to southward migration (indicated by a change in the daily patterns of their songs) can vary by at least four months. This variability is not random—later migration occurred in years with an earlier onset, later peak, and greater accumulation of ocean productivity on blue whales’ feeding grounds. This finding indicates that blue whales use flexible cues, perhaps including individual sensing of food availability and social information from other individuals (blue whale songs are audible over hundreds of kilometres) to match timing of feeding and migration with ecosystem processes. This flexibility could be key to survival of this endangered population in an era of rapid global change.