Eureka!: Do toads Have a Sixth Sense--AKA Proprioception?

This article ran in the Daily Hampshire Gazette on Friday, March 19, 2010.

By Kristin Palpini

There is now scientific research behind the old saying does a toad bump its rear when it hops?

Gary B. Gillis, a Mount Holyoke College biology professor, has concluded that terrestrial hopping toads have the ability to anticipate how hard they are going to land after a jump and adjust their muscles to absorb the impact accordingly.

Toads appear to be demonstrating prescient limb muscle activity and before Gillis' research, the ability had been observed only in mammals.

"We believe this data represents the first demonstration of tuned pre-landing muscle use in anurans (frogs and toads)," Gillis said. "It raises questions about how widespread this ability is among other species."

Technically, Gillis is talking about proprioception, a kind of sixth sense. Unlike exteroception, which is used to observe the outside world- smell, taste, touch, for example- proprioception is linked to internal sensors in joints that communicate movements of the body to the brain. This helps the body make preparations for things by say, tightening leg muscles ahead of the impact following a jump.

"The idea is that toads probably do the same thing," Gillis said.

To conduct his research Gillis, along with Mount Holyoke College students Trupti Akella and Rashmi Gunaratne, video recorded toads hopping in the lab, then slowed the images to observe minute details of the hop and land.

"It's actually well coordinated, like a gymnast sticking the landing," Gillis said. "Toads always stick the landing."

Researchers also attached fine wire electrodes to the toad's muscles so that they could observe how much electricity ran through their limbs during the process. Electricity was used as a surrogate for muscle contraction.

Gillis said more research is needed to determine whether their discovery is unique to toads or more common in anurans. There could also be implications in toad jumping research for people.

There are many questions about how the human body copes with an unpredictable environment, for example how the body would brace for the impact of missing a step in a stairway. If toads have the same prescient limb muscle activity as people, they could be a useful model for more detailed work on sensory feedback, Gillis said.

Related Links:

Gary Gillis Faculty Profile

Biological Sciences at MHC