The nocturnal Southeast Asian primate with eyes as large as, or sometimes larger than, its brain is the tarsier.
Tarsiers are tiny primates found on islands in Southeast Asia, including parts of the Philippines, Indonesia, and Malaysia. Their huge eyes are fixed in their sockets, so instead of rotating them like humans do, tarsiers can turn their heads roughly 180 degrees in either direction. This gives them an almost complete view of their surroundings while they wait motionless for prey.
Each eyeball is about 16 millimeters in diameter—remarkably large for such a small animal. Tarsiers are nocturnal hunters that eat insects, lizards, frogs, birds, and other small animals. They launch themselves between vertical trunks and branches using elongated ankle bones called tarsi, which give the group its name.
Tarsiers are often mixed up with lorises, lemurs, or bushbabies because all are small, night-active primates. They are distinct, however, and represent an ancient independent branch of primate evolution. Unlike many nocturnal animals, tarsiers lack a tapetum lucidum, the reflective retinal layer that produces eyeshine in darkness.