Could a whale swallow a person whole?

In the upcoming movie Whalefall, scuba diver Jay Gardiner finds himself in the path of a sperm whale that is chasing a giant squid. Accidentally tangled in a stray squid tentacle, Gardiner is pulled into the whale’s mouth as it slurps up its meal. Like Jonah and Pinocchio before him, he winds up in the behemoth’s stomach.

It’s not completely beyond the realm of possibility for a sperm whale (Physeter macrocephalus) to accidentally swallow a person. A “very big adult sperm whale” could do it, says comparative anatomist Joy Reidenberg of the Icahn School of Medicine at Mount Sinai in New York City. But it would take a full-grown bull reaching lengths of 18 meters or more, “bigger than most of the ones that we’re used to seeing,” says Reidenberg, who worked as a consultant on the movie.

Other large whale species would struggle to do so. Take the fin whale (Balaenoptera physalus). Though capable of reaching lengths of up to 26 meters, fin whales have a surprisingly narrow gullet. Reidenberg should know: Part of her job includes dissecting whale carcasses that have washed ashore. “I can barely get my arm down the throat,” she says. “There’s no way a human could be swallowed.” 

That’s because fin whales are baleen whales, a group that preys on some of the smallest animals on Earth: krill, small fish and plankton. These are strained from seawater using sievelike plates of baleen, which creates a fishy slurry. For the whales, “it’s kind of like drinking a thick milkshake.”

In a few rare instances, people accidentally get caught up by baleen whales going after prey; for instance, in 2019, a Bryde’s whale (B. brydei) briefly grabbed a wildlife photographer off the coast of South Africa before spitting him out. But such cases aren’t intentional human hunting. “The whale is just trying to have dinner, and [they] probably got in the way,” says marine biologist Shane Gero of Project CETI, an international nonprofit that studies sperm whale communication.

Sperm whales, though, prey on some of Earth’s largest creatures. Their favorites include giant and colossal squid — the latter of which can reach 14 meters long (with tentacles) and weigh hundreds of kilograms.

Based on how sperm whales’ smaller cousins, like belugas, feed in captivity, researchers think the behemoths suction up prey by depressing a bone in their throat called the hyoid. As the hyoid lowers, their tongue draws back. This works like a piston, creating an area of low pressure to draw water — and unsuspecting prey — into the whale’s mouth and widening its throat and the opening to the esophagus. Add to that the fact that a sperm whale has a larynx, or voice box, that is shifted to the left, making its throat much wider than those of other giant whales, enabling a big gulp.

But no one has ever observed this process in sperm whales. And researchers aren’t sure sperm whales actually swallow prey whole. When these elusive giants do surface with squid, it’s either with “literal chunks hanging out of their mouths or chunks floating behind them,” Gero says.

Swallowing people is also not in sperm whales’ nature, Reidenberg says. It makes for a thrilling movie night, but “these whales are very gentle when they’re around people who are not bothering them.” So while physiologically possible, their behavior and taste for deep-sea creatures make the events “very, very unlikely.” 

You’re also not likely to get hoovered up by a sperm whale by accident. These whales can dive more than two kilometers deep in search of a meal — far deeper than human divers can reach, Gero says. 

In fact, the only animal ever confirmed swallowing a human whole is the reticulated python (Python reticulatus). Several cases have been documented in Indonesia.

Like with other snakes, the grisly feat is possible due to the snakes’ flexible head and jaws. Multiple joints in their skulls allow for better movement. And soft, stretchy tissue in the lower jaw lets the snake maneuver its jaws over prey much larger than its head.

Still, “humans are very difficult for snakes to swallow,” says Bruce Jayne, a biologist at the University of Cincinnati. For a human, it would be important for a snake to swallow from head to toe, he says. Splayed limbs could anchor themselves in the corner of its mouth. Plus, humans’ broad, rigid shoulders can be hard for a snake to get their mouth around.

Instances of pythons eating humans are “extremely rare,” Jayne says. “Just because an animal has the physiological capacity to do something doesn’t necessarily mean that they will,” he says.