Newly recognized tricks help elephants suck up huge amounts of water

By | June 3, 2021

Whether or not it’s possible to teach an old elephant new tricks, a 34-year-old pachyderm at Zoo Atlanta has recently taught researchers a thing or two about how elephants suck up food and water with their trunks.

For one thing, an elephant doesn’t use its trunk as a simple straw. It can also dilate its nostrils to boost its trunk’s carrying capacity while snorting up water, researchers report online June 2 in the Journal of the Royal Society Interface. And that means it takes fewer snorts than expected to stock up on water that they use to drink and hose themselves down.

The surprise finding came courtesy of detailed measurements during feeding time, says Andrew Schulz, a mechanical engineer at the Georgia Tech in Atlanta. Other than aquatic creatures, not many animals other than elephants use a type of suction feeding that doesn’t depend on lung power alone.

Elephants are the only living land animals to evolve a long, boneless appendage like a trunk, says Schulz. A septum stretching the length of the trunk separates it into two nostrils. But detailed knowledge of what happens inside that muscular structure during feeding has been sorely lacking. So Schulz and his colleagues worked with zookeepers at Zoo Atlanta to take a peek.

An elephant’s trunk is iconic. But understanding what happens inside that muscular structure during feeding has been sorely lacking. Experiments with a patient pachyderm at Zoo Atlanta reveal its tricks for inhaling everything from small cubes of rutabaga to massive volumes of water.

Using ultrasound to monitor what was happening inside the trunk during feeding, the researchers put one of the zoo’s African elephants through her paces during the summer of 2018. In some trials, the elephant snorted up volumes of water, which in some cases had bran mixed in.

To the researchers’ surprise, says Schulz, the ultrasound revealed that each nostril’s available volume ballooned by as much as 64 percent, up from the trunk’s original capacity of about five liters (although the elephant used only a small fraction of this extra space). Flow rate of water through the trunk averaged about 3.7 liters per second, or the equivalent of the amount of water pouring out of 24 shower heads at once.

A layer of chia seeds along the bottom of a container of water helped researchers study just how fast an African elephant sucks water up into her trunk.A.K. Schulz et al/J. Roy. Soc. Interface 2021

In other trials, the elephant was offered small cubes of rutabaga of various sizes. When offered just a few cubes, the elephant picked them up with the prehensile tip of the trunk. But when offered piles of cubes, she switched into vacuum mode. Here, the nostrils don’t expand, but rather the elephant breathes in deeply to hoover up the food.

Based on the amount and rate of water snuffed up by the elephant, the researchers estimated that airflow through the narrow nostrils could at times exceed 150 meters per second — more than 30 times as fast as a human sneeze, Schulz says.

 The internal structure of an elephant’s trunk — except for the nostrils — is similar to an octopus’s tentacle or a mammalian tongue, says William Kier, a biomechanicist at the University of North Carolina at Chapel Hill who was not involved with this study. The trunk’s intricate musculature and lack of joints “create a great diversity, complexity and precision of movement,” he says.

“How elephants use their trunks is pretty fascinating,” says John Hutchinson, a biomechanicist at the Royal Veterinary College in Hertfordshire, England, also not involved with this study (SN: 11/16/15). And although engineers have already designed robotic devices based on an elephant’s trunk, the team’s new findings may yield even wilder designs, he says. “You never know where bioinspiration will lead.”