At first, Rundus and his team were not sure if the hot squirrel tail was simply due to squirrels becoming physiologically aroused in the face of a threat.
To test this possibility, the scientists filmed 12 mother squirrels defending their pups against non-venomous gopher snakes. During these conflicts, the mother squirrels rarely emitted infrared.
"While adult female squirrels facing both rattlesnakes and gopher snakes bushed out their tails and flagged them in a similar manner, we now know that the tail's infrared serves as a targeted defense against rattlesnakes," Rundus said.
He and his team also created a lifelike, odiferous squirrel robot, which they presented to 14 adult northern Pacific rattlesnakes. The snakes were placed in a testing chamber containing a simulated squirrel burrow that contained a warm (but dead) rat pup.
When the rattlesnakes slithered toward the dead rat, out would come the squirrel robot, wagging its tail. Wags combined with infrared were much more effective at warding off the snakes.
Owen Maercks, a snake expert and co-owner of the East Bay Vivarium in California, told Discovery News that "while we tend to think of rattlesnakes as perfect predators, squirrels must have evolved infrared as a counter-offensive against the snake's infrared-sensing tactics."
"Snakes also are not bright animals," Maercks said. "By contrast, squirrels are strategists. I watch them chatter, flick their tails and show their butts to my three little dogs in our backyard."
"The squirrels taunt the heck out of potential predators," he added. "It even seems like they enjoy outwitting them."
Rundus and his colleagues don't yet know the mechanism that allows the squirrels to emit the infrared. He and his colleagues think warm body core blood moves to the tail region, but further testing is needed to confirm that speculation.
Related Links:
A NASA primer on dark matter.
Zoogoer magazine
Flying snakes!
San Francisco's Exploratorium
