What are signs of animal life?
Anything moving. Trees,rivers,grass, etc. Just look closely and you'll see.
Well it depends on what you mean by "signs". Almost every single animal on the planet would and could identify some sort of sign given either by another animal of the same species or the sign (warning) of a predictor of the animal. So in order to answer the question correctly, or most accurate would be to be more specific about your meaning of "signs" .mjc..