Posted: February 5, 2010
Humans may not have a leg up on toads, at least not when it comes to jumping and landing, according to new research by MHC associate professor of biology Gary Gillis. In a paper published February 3 in the Royal Society journal Biology Letters, Gillis shows that toads, like humans, are capable of anticipating when and how hard they’re going to land after a jump and adjusting the activation of muscles important for absorbing impact accordingly.
The paper, titled "Do Toads Have a Jump on How Far They Hop...," was authored with two undergraduates, Trupti Akella '09 and Rashmi Gunaratne '10.
Until now, such prescient limb muscle activity has only been demonstrated in mammals, but Gillis and his team showed that hopping toads can alter both the intensity and timing of activity in muscles used to stabilize their forelimbs on impact. In long hops, when impact forces are known to be higher, elbow muscles exhibited more intense activity just prior to landing than during short hops. In addition, one major elbow muscle was always activated at a fixed interval prior to landing in all hops, regardless of distance, suggesting that toads not only gauge how hard they’re going to hit the ground, but also anticipate precisely when that will happen.
“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 and how important feedback from various sensory systems--e.g., vision--is for mediating this ability."
This coming summer, Gillis and his students will be conducting similar experiments on different species of frogs to determine if their findings are unique to toads or more common in anurans. They will also be making a blindfold for toads so they can test Gillis's hypothesis that vision is necessary for these animals to anticipate the timing and magnitude of impact.
Gillis, who has been a member of the College faculty since 2002, specializes in research on the biomechanics and neuromuscular control of animal locomotion.