for National Geographic News
California ground squirrels warm up their tails to ward off heat-sensitive rattlesnakes, researchers have discovered.
When confronted by a squirrel waving a "hot" tail over its head, northern Pacific rattlesnakes will often cease their predatory behavior and go on the defensive, according to a new study led by researchers at the University of California, Davis.
It's not that a squirrel's tail—heated or not—poses any threat to a rattlesnake, biologists say.
Instead the hot tail signals the readiness of adult squirrels to defend their young from a rattlesnake attack.
This so-called thermal signaling is so effective because rattlesnakes are highly sensitive to heat. They use a specialized sensory organ to detect the infrared radiation—or heat—given off by their small mammal prey.
(Related: Snakes on a Page: Full Serpent Coverage" [August 14, 2006].)
The heat "increases the conspicuousness of the squirrel's tail-flagging display," said study lead author Aaron Rundus, now at the University of Nebraska-Lincoln.
"This display signals to the snake that it has been detected, and that it is likely to be harassed by the squirrel and other[s] in the vicinity."
The squirrel likely warms its tail by increasing blood flow from its body to the normally cooler tail region, said study co-author Donald Owings of UC Davis.
The study appears today in the online version of the journal Proceedings of the National Academy of Sciences.
When snakes are around, adult California ground squirrels want to make themselves noticed.
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