An elephant’s trunk is a wonder of evolution. Gentle, yet dextrous, it can pick up solid items, help them communicate, and be a helpful showering tool. Inside, 1,000 whiskers give the large animals a very strong sense of touch to compensate for poor eyesight and thick skin. They are also more like a cat’s whiskers and have a design that engineers consider to be “intelligent,” according to a study published today in the journal Science.
To examine how the elephant trunk whiskers work, engineers from Max Planck Institute for Intelligent Systems, neuroscientists from Humboldt University of Berlin, and materials scientists at the University of Stuttgart in Germany joined forces. They hoped to understand how the whiskers are shaped (or their geometry), how porous they are (porosity), and how soft they are (material stiffness). Initially, the team expected that the whiskers would be more similar to the tapered whiskers of mice and rats. These rodent whiskers have a circular cross-section, are completely solid throughout, and have approximately uniform stiffness.
They used micro-CT scanning to measure the 3D shape of several whiskers and found that elephant whiskers are actually quite different from rat whiskers and more like the ones found on domestic cats. Elephant trunk whiskers are more thick and blade-like, have a flattened cross-section, a hollow base, and several long internal channels that look more like the structure of sheep horns and horse hooves. Having a more porous build reduces the whisker’s mass and provides impact resistance—which helps them eat hundreds of pounds of food without damaging their whiskers. Not damaging these whiskers is vital since they do not grow back.
Additionally, the whiskers on domestic cats’ faces and inside of elephant trunks have stiff bases that transition to soft rubber-like tips that work differently than the uniformly stiff whiskers seen on mice and rats. The stiff-to-soft transition in the whiskers is called a functional gradient. It keeps them in tact and helps let the elephant determine what it is feeling. The team believes that elephant whiskers’ unusual stiffness gradient helps them know precisely where an object is coming into contact along each of their 1,000 trunk whiskers.
In other words, the stiffness gradient helps explain how they can pick up a brittle tortilla chip without breaking it or precisely pick up a peanut. The team also compared the trunk whiskers to elephant body hair.
“The hairs on the head, body, and tail of Asian elephants are stiff from base to tip, which is what we were expecting when we found the surprising stiffness gradient of elephant trunk whiskers,” Andrew K. Schulz, a study co-author and postdoctoral researcher at Max Planck Institute for Intelligent Systems, said in a statement.
The team of researchers worked to prepare elephant whiskers from various parts of the elephant’s trunk for advanced microscopy and characterization methods. Image: MPI-IS/W. Scheible.
To better understand how the changing stiffness along an elephant’s whisker would affect touch sensing, they created a physical “whisker wand” with a 3D printer. The wand had a stiff, dark base and a soft, transparent tip and helped the researchers get a sense of what an elephant trunk feels through its whiskers.
Study co-author and engineer Katherine J. Kuchenbecker carried the whisker wand with her when walking through hallways, gently hitting columns and railing.
“I noticed that tapping the railing with different parts of the whisker wand felt distinct—soft and gentle at the tip, and sharp and strong at the base,” Kuchenbecker recounted. “I didn’t need to look to know where the contact was happening; I could just feel it.”
Katherine J. Kuchenbecker (left) and Andrew K. Schulz (right) with the 3D-printed whisker wand that helped the research team understand how a functional gradient of material stiffness could facilitate contact sensing in elephant and cat whiskers. Image: MPI-IS/W. Scheible.
After testing the whisker wand, they used computational modeling to assess how the unique geometry, porosity, and stiffness gradients they had measured affect how an elephant’s whisker responds when it comes in contact with an object. They found that the transition from a stiff base to a soft tip makes it easier to feel where something is touching along the whisker, allowing the elephant to react appropriately and carefully manipulate delicate objects.
“It’s pretty amazing! The stiffness gradient provides a map to allow elephants to detect where contact occurs along each whisker,” Schulz said. “This property helps them know how close or how far their trunk is from an object…all baked into the geometry, porosity, and stiffness of the whisker. Engineers call this natural phenomenon embodied intelligence.”
The team hopes that these insights can be applied to robotics and other intelligence systems. A sensor with an artificial elephant-like stiffness gradient could help give a future robot more precise information through its simple yet intelligent design.
The post Elephants are smart. So are their whiskers. appeared first on Popular Science.
