"Can animals talk to other animals?" Yes, obviously.

"Can animals talk to other animals?" Asks Maggie Koerth-Baker on BoingBoing.net.  "This question—from an Anon's 6-year-old cousin—is familiar to anyone who's ever been caught up in the poignant friendship of a cartoon fox and a cartoon hound. Obviously, their real-life equivalents aren't sitting down to chat, vocally, about Yeats over a nice cup of tea. But if you drop the human pretension, and start thinking of communication as a simple exchange of information, you'll see cross-species conversations happening, experts say.…We humans tend to think of communication as solely about formal language—preferably spoken. Instead, animals use things like movement, posture and even pee—as well as sounds—to share concepts like, "I want to play," or messages like, "There's food over here." As long it makes sense, communication has happened."

http://www.boingboing.net/2010/03/02/science-question-fro-6.html
http://acp.eugraph.com/
http://www.zoosemiotics.helsinki.fi/