Source: http://news.yahoo.com/s/ap/20070814/ap_on_sc/hot_tail
Calif. squirrels heat tails for
defense
By RANDOLPH E. SCHMID, AP Science Writer
Tue Aug 14, 5:18 PM ET
WASHINGTON - California ground squirrels have learned to intimidate
rattlesnakes by heating their tails and shaking them
aggressively.
Because the snakes, which are ambush hunters, can sense infrared
radiation from heat, the warming makes the tails more conspicuous
to them signaling that they have been discovered and that the
squirrels may come and harass them, explained Aaron Rundus, lead
author of a study in this week's online edition of Proceedings of
the National Academy of Sciences.
The tail "flagging" places the snakes on the defensive, he
said.
Adult squirrels are not the snakes' prey, Rundus said in a
telephone interview. The adults have a protein in their blood that
allows them to survive the snake venom, and they have been known to
attack and injure snakes, biting and kicking gravel at them.
Rather, the snakes are looking for immature squirrels, which they
can kill and eat, said Rundus, who did the research while at the
Animal Behavior Graduate Group at the University of California,
Davis.
Researchers are not sure just how the squirrels cause their tails
to heat up, but they think it may be by shunting warm blood from
the body core into the tail.
"It's such a new discovery that it leaves a lot of questions," he
said.
But apparently it isn't just a reflex, because they only do it with
rattlesnakes.
Confronted by gopher snakes, which can't sense heat, the squirrels
wave their tails vigorously, but don't bother to heat them
up.
So how did they discover that the squirrels heat their tails?
The researchers were studying how squirrels reacted to various
predators and noticed that with rattlesnakes they waved their tails
even more in dark conditions than in the light.
That prompted the researchers to view the encounters using an
infrared camera, and they discovered the squirrels' tails were much
warmer than normal when dealing with rattlesnakes.
Learning more about these complex communication methods among
animals may help improve understanding of how complex human
communications have evolved, Rundus said.
He said it serves as a reminder that to understand more about
animal life, we need to pay close attention to how animals act.
"There is potentially a lot going on out there that we're not aware
of," he said.
