Biology is Cool: Infrared Signaling by Squirrels

I just love things like this.  An open-access
article in title="Proceedings of the National Academy of Sciences">PNAS
reports on a previously-unknown method of signaling employed by
squirrels.  



The squirrels have a way of enhancing a tail-flagging movement with an
IR signal.  The IR enhancement is optional.  It turns
out they use it when confronted by rattlesnakes that are sensitive to
infrared.  



When confronted by snakes that are not IR-sensitive, they do not use
the IR trick.



The rattlesnakes that see the IR signal are more likely to adopt a
defensive, as opposed to a predatory, posture, when they get the IR
signal.



OK, now for the weird part: one of the authors is a professor of
mechanical and aeronautical engineering.








Why have an engineer?  Are ordinary biologists
incapable of understanding IR signaling?  Of course they
understand it.  But the key is in the way the hypothesis was
tested:



Why have an engineer?  Are ordinary biologists
incapable of understanding IR signaling?  Of course they
understand it.  But the key is in the way the hypothesis was
tested:



Experimental playbacks with a biorobotic
squirrel model reveal this signal's communicative function. When the
infrared component was added to the tail flagging display of the
robotic models, rattlesnakes exhibited a greater shift from predatory
to defensive behavior than during control trials in which tail flagging
included no infrared component.



Building a biorobotic squirrel!  That is why they needed an
engineer.
 Looks just like the real thing!




i-c7e7d943803c6373a9e20941d4f16a12-robot-squirrel.jpg



(source)


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And the source of the IR is? (I presume they're meaning heat...)

Is the squirrel passing flatus? That would be warm. Kind of makes sense that being around a snake might cause a disruption of sphincter control...

Cool! But I wonder what is the cost associated to having a sudden blood flow in the tail? I guess it must be strong enough for the IR-signal to be specifically triggered by rattlesnakes and not by other snakes unsensitive to IR.

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