A meal with mammals from space
Behind the biomechanics of how baleen whales eat.
The laws of physics dictate that the bigger you get, the less maneuverability you have.
Yet the biggest animal on earth — the blue whale — can do a 360-degree barrel roll. “Sometimes they do a 180 pitch flip — and they can do it in sync with each other,” says Jeremy Goldbogen, a marine physiologist at Stanford University. “The scope of their behavioral maneuverability is incredible.”
“We joke that these guys are from space because they’re totally crazy,” Goldbogen says. “They have huge feeding sacks and unique jaws that no other mammals have.”
Blue whales also have an alien-like tongue that can invert itself, allowing the entire area from the whale’s mouth to its belly button to expand. This oropharyngeal cavity (or feeding pouch) is encased in ventral groove blubber. While many other cetaceans have stiff blubber, this accordion-like tissue has the unique ability to expand enough for the blue whale to engulf one and a half times its body mass.
Goldbogen’s research includes analyzing videos of blue whales feeding (recorded via suction cup tags that adhere to a whale’s back for roughly 24 hours.)
Now, as part of this research team in Antarctica, Goldbogen hopes they can find and tag enough minke whales to learn as much as he and his colleagues currently know about blue whales.
While the largest mammal on earth can engulf up to 150 percent of its body mass, little minkes can only gulp 20 to 60 percent. But what they lack in mass, minkes make up for in speed and efficiency — they can lunge, filter, and reload much quicker, taking six or seven gulps in a minute.
So it comes down to quantity over quality — minkes take more, smaller bites, and blue whales take fewer, larger bites. But both species face a precarious balancing act between energy exertion and consumption.
“If they take a big gulp and swallow more krill, they may get more energy,” Goldbogen says. “But their ability to stay under water may be reduced.”
For humans, accustomed to stuffing ourselves while sitting at a table or vegging out on the couch, it may be hard to comprehend that eating a meal could be a highly aerobic activity. Imagine jumping into a pool, swimming as fast as you can, and opening your mouth to suck down a bunch of shrimp — all on one breath of air.
Whales are obviously better built for this activity, but they’re still mammals functioning on limited oxygen reserves while exerting huge amounts of energy.
“It’s like doing suicide sprints while holding your breath,” Goldbogen says.
When it comes to the biomechanics of whales, balancing energy exertion versus consumption is one of the major questions.
“These are the biggest animals that have ever lived and we have no idea how much energy they need,” says Dave Cade, a PhD student in Goldbogen’s lab and another member of the research team in Antarctica.
“We try to calculate how much energy they’re using based on the amount of movement, and the physics of how they move,” Goldbogen says. “Can we refine those measures and improve our estimates?”
That will be one of the goals over the next two weeks.