Interesting example of communication

[Russ Abbott]

Some squirrels use infrared radiation to signal rattlesnakes not to attack their young. They don't send the same signals to other snakes that aren't able to sense infrared.  See http://news.nationalgeographic.com/news/2007/08/070813-squirrel-snake.html  and  http://www.pnas.org/cgi/reprint/104/36/14372. This illustrates that these squirrels managed to evolve (a) the ability to send infrared signals to snakes and (b) to "know" to which snakes to send those signals.

-- Russ