It's not just humans who notice optical illusions; certain animals do too, and they often use it to their advantage.

A Mississippi mother shot an escaped monkey near her home after a truck crash released 21 research primates. Two monkeys ...

Four rival families - leopards, hyena, wild dogs and lions - all fight to claim a remote Zambian paradise as their home. Who ...

A troop of macaques escaped one of the largest primate-breeding facilities in America. Now a strange coalition of ...