For most people picking up shed cat whiskers is a chore, but for science faculty member Eric Kramer, it was an inspiration. After cleaning some of his cat’s whiskers, Kramer observed they each had a tapered shape. He wondered if it was similar to other whiskers, and if so, what made that shape important? “With the exception of primates, nearly all mammals have whiskers,” Kramer explains. “The question was whether there was some evolutionary advantage to the tapered shape.”
While mulling these questions in 2007, then undergraduate Chris Michael Williams ’04 (now a graduate student at MIT) approached him about research opportunities at the College. After Kramer suggested they might explore the mechanical properties of cat whiskers, Williams signed on. “Of all of the possibilities for projects,” Williams recalls, “this one certainly surprised me.”
The pair first reviewed previous whisker research conducted on rats, which typically traces brain activity linked to whiskers. However, Kramer and Williams were interested in the functional importance of a whisker’s shape and elastic properties—a deviation from the traditional whisker research that focuses on biological questions. “Biologist usually study rat whiskers as a model system for sensory neurobiology,” Kramer explains. “But Chris and I were coming from a different direction. We were asking different questions.”
In order to test the mechanical properties, Williams designed an experiment using a handful of simple lab tools—a digital caliper, a microgram balance, and some clamps. He then sent a campus-wide email asking for whisker sample donations. “We got more donations than we needed,” Kramer laughs. “There are a lot of cat people at Simon’s Rock.” They took digital photos to measure the shape and taper. Then, using Williams’s handmade apparatus, they began to test the mechanical properties.
They discovered that when force was applied to the tip of the whisker, it would behave differently than when it was applied near the base. A surprise, Williams says, along with the resilience of the whiskers: “Given the relatively large deflections and forces near the base, the whiskers typically did not break. I was aware that whiskers were fairly strong, but their elasticity was unexpected.”
Their findings clarify how the tapered whisker shape helps cats and other mammals detect distant objects and surface textures. In addition, Williams says, “The consistency of this shape between whiskers of different species suggests that this shape did not merely occur by chance, but had a specific purpose that nature preserved over time.” Kramer adds that whisker evolution has been ongoing for 120 million years---“They’re as old as the first mammals”—observations that anchor their co-authored paper, “The Advantages of a Tapered Whisker,” which appeared in Public Library of Science ONE in January.
Kramer hopes that this finding will further whisker research and help shed new light on important biological questions. And for the non-scientific community? “I hope people with animals will begin to understand that they should not cut their animal’s whiskers. Humans assume they are no more important than eyebrows or eyelashes, when in fact ours, and other research, proves that whiskers are much more akin to sensory organs like eyes or ears.”