One More Reason to Admire Elephant Trunks
By Katherine J. Wu │The Atlantic│6 min
New research confirms that elephant trunks don’t just blow—they can also suck.By
The trunk of an African elephant is an evolutionary marvel. Clocking in at weights well over 200 pounds, it ripples with thousands of individual muscles that help the superlong schnoz lift barbells, uproot trees, and fling bothersome lions into the air.
A tortilla chip is an embarrassment of engineering. It weighs a fraction of an ounce and can measure less than a millimeter thick; it is so woefully fragile that the heft of a guinea pig or a generous scoop of guacamole could easily snap it in two.
And yet a union between chip and trunk is not as impossible as it might seem. Andrew Schulz, an engineer at Georgia Tech, and his colleagues have caught such an improbable pair on camera, reconciling the absurd imbalance between them, and described it in a paper published today in the Journal of the Royal Society Interface. When offered a tortilla chip, they found, an elephant will use its trunk to deftly suctionthe salty treat into its grip. The chip stays intact (at least until it’s deposited into the elephant’s mouth); in the video, you can hear the researchers cheer.
Elephants don’t encounter many chips in the wild, or even that often in captivity. But that’s not necessarily the point. The tortilla-chip experiment, along with several others conducted by Schulz’s team, helps illustrate the biomechanical properties of trunks, which vacuum up foods the animals can’t otherwise easily reach. African-elephant noses, the team found, can inhale air at speeds of more than 335 miles per hour, faster than a Bugatti, faster than most bullet trains, faster than a dive-bombing peregrine falcon. Elephants are kind of, sort of, accomplishing a type of airbending—using air as a tool to manipulate their surroundings, a rare skill among land animals. “It’s a way for an animal to move food toward its body without even touching it,” Rita Mehta, an evolutionary biologist at UC Santa Cruz who wasn’t involved in the study, told me.
Researchers were tabulating the talents of trunks long before their encounters with tortilla chips were captured on camera. (A quick note: The paper refers to its corn-based experimental fodder as “tortilla chips,” but technically they were small tostadas, according to Schulz.) Trunks are über-extended noses that allow elephants to breathe, call, fight, grasp, sense, and smell, all with the same piece of anatomy. They’re tipped with fingers deft enough to pinch individual blades of grass; the olfactory machinery they contain is so sensitive that it detects TNT better than most bomb-sniffing dogs. The Elephant Ethogram, an archive of African-elephant behaviors hosted by the organization Elephant Voices, documents no fewer than 250 separate trunk-related actions that elephants engage in, from signaling to snorkeling to pinching parents’ genitals to get their attention. “The trunk is a magnificent apparatus,” Joyce Poole, a co-founder and co-director of Elephant Voices, told me. Elephant trunks were already one of the strangest and most accomplished limbs in the annals of biology; the calculations from Schulz’s team now confirm that they also suck real hard.
Some of that suckage isn’t necessarily news. Researchers have known for many years that elephants’ tubelike snoots can siphon up water, then deposit it into the mouth or spray it across the back. And at least as far back as the 1800s, naturalists such as Charles Darwin were suggesting that elephants could blow air to push objects just beyond their reach; a 2016 study confirmed that the animals could use the tactic to nudge food around their enclosures. But the mechanical how of these behaviors, Schulz told me, has remained mostly mysterious. And although there had been some chatter about air going out, few people were asking how it came in.
The Georgia Tech team decided to investigate with the help of keepers at Zoo Atlanta and a now-38-year-old African elephant named Kelly. When offered frustratingly flat objects such as chips, Kelly reliably used suction to get an easier grip on them. But she was judicious with other snacks, and would vacuum up small cubes of rutabaga only when there were too many for her to easily pluck them up one by one with her fingers.
To measure the strength of Kelly’s inhales, the researchers filmed her slurping up a slurry of chia seeds mixed into water. By tracking the movements of the seeds frame by frame, Schulz and his colleagues could visualize how quickly water was entering her nostrils. Kelly’s six-foot-long trunk, they found, could expand to comfortably fit more than 5.5 liters of liquid at once, enough to account for every drop of blood in an average adult human’s body. Kelly sucked up that volume in about a second and a half.
The researchers crunched the numbers to approximate how air, rather than water, would flow into the same structure. Their estimate of 150 meters per second, or 335 miles per hour, is about 30 times as fast as a typical human sneeze. Elephant air expulsion, Schulz suspects, might be even faster, though he’s not sure by how much. (It would also, he pointed out, produce a lot of snot.)
Poole, who wasn’t involved in the study, said that food suctioning might be somewhat uncommon in the wild, where snuffing up vegetation off the ground could ferry all manner of dirt and crud into the airway as well. (Consider also just how difficult it would be to pick a six-foot-long nose.) But elephants are capableof executing this strategy, and it probably gets more play in zoos, where their meals are carefully cut and portioned. “All these little bits are given to them in captivity, for convenience,” Caitlin O’Connell, an elephant researcher at Harvard who wasn’t involved in the study, told me.
Schulz’s team argues that the sucking shenanigans of elephant trunks count as a form of suction feeding—a technique that many fish use to vacuum up their meals. Some of the experts I talked with were less sure. An originalist interpretation of suction feeding might hold that an animal must suck and swallow with the same orifice, as many fish do: They can expand the highly mobile bones in their skull, generating a pressure gradient that draws water—and the stuff living in it—into their waiting mouth in as little as six milliseconds. Suction feeding is also a staple among certain marine mammals, such as whales and and seals, and, arguably, all animals that suckle from their mother after birth. Even some seabirds seem to have some liquid-vacuuming prowess.
Elephants and their trunks are outliers. Their noses are middlemen, and suctioners of convenience; elephants are lucky enough to do most of their feeding on land, where simply reaching out and grabbing a morsel of food is easy. (Animals that hunt or forage in the sticky, viscous fluid that is water often end up pushing their meals away when they move toward them.) The elephant approach to suctioning is “definitely different than everything else,” Mehta said.
But these unconventional quirks might make trunks all the more remarkable. And the exclusive club of suck doesn’t have to be anatomically strict: Ariel Camp, a fish suction-feeding expert at the University of Liverpool who wasn’t involved in the study, points out that some of the world’s most impressive suction feeders are carnivorous plants called bladderworts, which suction their prey into traps at blistering speeds, even though they don’t share the vertebrate body plan.
Schulz, who said he personally “cannot eat a tortilla chip without breaking it,” isn’t agonizing over the differences. (He admitted that he has yet to try suctioning up a chip with his nose.) His next goal is to more thoroughly map the internal structure of the elephant trunk, and to put more mathematical weight behind all that the appendage can accomplish. “It’s a muscular multi-tool,” Schulz said. “It pushes all of the extremes of what we understand animals to be able to do.”