Guppies can be fooled by optical illusions into believing objects are smaller or larger than they really are. This suggests they might not always make the best choices in their natural environment.

Guppies are a small, pretty species of fish that are extremely popular for home aquariums. While they’re fun in captivity, in the wild they can cause major trouble. Native to South America, guppies ...

When Robert Heathcote dips his head into the rivers of Trinidad, he’ll often see little black dots moving through the water, even when it’s murky. Those dots are the eyes of small, inch-long fish ...