Female convict cichlid fish turned from optimists to pessimists when separated from their chosen partners.
New study reveals how baby hoatzin birds are able to move like four-legged animals, thanks to unique claws on their wings.
Some male animals may evolve weak immune responses so they can give their mates diseases.
Newly-discovered fossil deposit contains more than 50 unknown species from the Cambrian Explosion, when most complex body plans appeared.
Indoor temperature and moisture in the U.S. is closer to climates in Africa than to anywhere else on Earth.
When the foraging sea mammals crack shells to collect food, they produce distinctive evidence.