Elephants’ trunks “act like suitcases” by expanding to create more space, research has found.
The animals can dilate their nostrils, allowing them to store up to nine litres of water and can also suck up three litres per second, a speed 50 times greater than a human sneeze.
A study by the Georgia Tech College of Engineering sought to better understand the physics of how elephants use their trucks to move and manipulate air, water, food and other objects – while seeking to learn if the mechanics could inspire the creation of more efficient robots that use air motion to hold and move things.
While octopus use jets of water to move and archer fish shoot water above the surface to catch insects, the researchers found the pachyderms are the only animals able to use suction on land and water.
“An elephant eats about 400 pounds of food a day, but very little is known about how they use their trunks to pick up lightweight food and water for 18 hours, every day,” said Georgia Tech mechanical engineering PhD student Andrew Schulz, who led the study. “It turns out their trunks act like suitcases, capable of expanding when necessary.”
Mr Schulz and the Georgia Tech team worked with vets at Zoo Atlanta to study elephants as they ate various foods.
They observed how the elephants grabbed and collected large rutabaga cubes, but sucked up smaller cubes with a loud vacuuming sound before transferring the vegetables to its mouth.
To learn more about this suction, the researchers gave the elephants a tortilla chip and measured the applied force.
Sometimes the animal pressed down on the chip and breathed in, suspending it on the tip of its trunk without breaking it, while other times the elephant applied suction from a distance, drawing the chip to the edge of its trunk.
“An elephant uses its trunk like a Swiss Army Knife,” said David Hu, Mr Schulz’s advisor and a professor in Georgia Tech’s George W Woodruff School of Mechanical Engineering.
“It can detect scents and grab things. Other times it blows objects away like a leaf blower or sniffs them in like a vacuum.”
By watching elephants inhale liquid from an aquarium, the team were able to time the durations and measure the volume to find that in just 1.5 seconds the trunk sucked up 3.7 litres, or the equivalent of 20 toilets flushing simultaneously.
An ultrasonic probe used to take trunk wall measurements found an elephant is able to dilate its nostrils up to 30 per cent by contracting its inner trunk muscles, decreasing the thickness of the walls and expanding its nasal volume by 64 per cent.
“At first it didn’t make sense: an elephant’s nasal passage is relatively small and it was inhaling more water than it should,” said Mr Schulz.
“It wasn’t until we saw the ultrasonographic images and watched the nostrils expand that we realised how they did it. Air makes the walls open, and the animal can store far more water than we originally estimated.”
Based on the pressures applied, the team suggest elephants inhale at speeds that are comparable to Japan’s 300-mph bullet trains.
Mr Schulz said these unique characteristics have applications in soft robotics and conservation efforts.
“By investigating the mechanics and physics behind trunk muscle movements, we can apply the physical mechanisms — combinations of suction and grasping — to find new ways to build robots,” he said.
“In the meantime, the African elephant is now listed as endangered because of poaching and loss of habitat. Its trunk makes it a unique species to study. By learning more about them, we can learn how to better conserve elephants in the wild.”
The research paper “Suction feeding by elephants” is published in the Journal of the Royal Society Interface.