In relation to body size, tarsiers have the largest eyes of all mammals. Each eye is larger than the brain.

Tarsiers are nocturnal, eat insects and can turn their heads almost completely backwards. Tarsiers live in Indonesia and the Philippines.

Depending on the species and area, tarsiers live either as singles – where the territories of the females and males overlap – or monogamously. Occasionally, tarsiers also live in groups of several males and females.