The nocturnal primate with the largest eyes relative to its body size is the tarsier.
Tarsiers are tiny primates native to Southeast Asia, including the Philippines, Sulawesi, and nearby islands. Their enormous forward-facing eyes gather as much light as possible for hunting at night. Each eye is roughly comparable in size to the animal’s brain, making it one of the most striking examples of nocturnal adaptation among mammals.
Unlike human eyes, a tarsier’s eyes cannot swivel in their sockets. To compensate, the animal can rotate its head by almost 180 degrees. Its sensitive ears also help detect insects and other prey moving through dense vegetation.
A common mix-up is the bushbaby, another small nocturnal primate with large eyes. Bushbabies are famous for their night vision, but tarsiers are generally recognized for the greatest eye-to-body ratio among mammals. Tarsiers also have elongated ankle bones, powerful hind limbs, and the ability to leap several times their body length.