Lunging for lunch

Eating only “works” if you take in more energy than you expend during the process. Some organisms expend particularly large amounts of energy while foraging, like lunge-feeding baleen whales, which accelerate their large body masses (like, seriously large, up to blue whale-sized masses) toward aggregates of fish or krill prey. These whales don’t only need to eat enough to make up for the cost of foraging–they also need to put on some fat to get through the breeding season and the less-bountiful winter. However, these whales can also engulf massive amounts of food in a single lunge and often exhibit very high feeding efficiency.

Potvin et al. 2021 in IOB analyzed the feeding dynamics of large, lunge-feeding whales to learn how the extremely large amount of energy required by lunge-feeding and the extremely large amount of food acquired by lunge-feeding can result in variable feeding efficiencies, depending on the dynamics of the lunge.

Humpback whale feeding. Photo by David Csepp, public domain courtesy of NOAA.

Potvin et al. 2021 used biotag data on swim speed from humpback and blue whales to analyze one relatively low energy method of lunge-feeding called coasting engulfment. In this method, the whale coasts through the prey and decelerates after an initial high speed. The acceleration happens before the mouth is opened to feed.

(A higher-energy alternative method is when the whale accelerates into the aggregate of prey with the mouth open, which requires overcoming a lot of additional drag.)

They found that the feeding efficiency of lunge-feeding in these very large whales can be greatly impacted by the density of the prey aggregation within the water and the speed at which the lunge occurs. Faster speeds result in reduced feeding efficiency.

From Potvin et al. 2021: Feeding efficiency in a blue whale depends on the speed of the lunge when the mouth opens (Uopen) and the density of the prey aggregate as well the duration of the lunge.

So why do lunge-feeding whales ever increase their lunging speed if it results in decreased feeding efficiency? The authors suggest a few ideas for future study to clarify this question, including that faster lunges could allow for more dives and thus greater energy intake, even if each lunge is more inefficient. Although this is an important step in improving our understanding of the dynamic and energetic mysteries of lunge-feeding, the authors note that there is still much to learn! I’m looking forward to seeing their recommendations implemented in future manuscripts!

By Katie Stanchak

Katie Stanchak is a Postdoctoral Scholar in the Department of Biology at the University of Washington. Her interests include animal locomotion and the evolution of novel anatomical elements.

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