Confronting assumptions about prey selection by lunge-feeding whales using a process-based model

The relative energetic benefits of foraging on one type of prey rather than another are not easily measured, particularly for large free-ranging predators. Nonetheless, assumptions about preferred and alternative prey are frequently made when predicting how a predator may impact its environment, adapt to environmental change, or interact with human activities. We developed and implemented a process-based model to investigate the potential energetic benefit (PEB) of in situ foraging opportunities in rorqual whales. The model integrates and evaluates the energetic importance of measured prey patch characteristics (prey distribution, energy content and predator avoidance) and predator characteristics (morphometrics, foraging tactics and feeding rates). We applied the model to test the assumption that hatchery-released juvenile salmon are an “easy meal” for humpback whales compared to more common prey, herring and krill. In eleven out of the thirteen foraging situations considered,...