Which primate has the biggest eyes for its size?
Quick answer
The tarsier has the largest eyes relative to body size of any mammal. Each eyeball is roughly as big as its brain. These small, nocturnal primates live in the forests of Southeast Asia, including the Philippines, Borneo and Sulawesi. Their eyes can’t move in their sockets, so tarsiers turn their heads up to about 180°.
Key facts
- Body length
- About 9–16 cm, plus a much longer tail
- Weight
- About 80–160 g
- Range
- Philippines, Indonesia, Malaysia, Brunei
- Active
- At night (nocturnal)
Eyes built for darkness
| Feature | Detail |
|---|---|
| Eye size | Each eyeball is about 16 mm across, roughly as big as its brain |
| Fixed eyes | Too large to move; the tarsier turns its head instead |
| No reflective layer | Unlike cats, tarsiers lack a tapetum, so huge eyes help gather light |
If humans had eyes that big relative to their bodies, each would be about the size of a grapefruit.
The land animal with the largest eyes in absolute terms is a bird; see which land animal has the largest eyes.
The only fully carnivorous primate
Tarsiers eat only animals: insects, spiders, lizards and sometimes small birds or snakes. They hunt by leaping from branch to branch, sometimes over 40 times their body length, and grabbing prey with their hands. Their long ankle bones, the tarsus, give them their name.
Secret ultrasound calls
A 2012 study found that Philippine tarsiers communicate using ultrasound, calls at around 70 kHz, far above the range of human hearing. This may let them talk without alerting predators or prey.
Sensitive to stress
Tarsiers are shy and easily stressed. In captivity, they often do poorly. Conservationists in the Philippines advise visitors to see them only at reputable sanctuaries such as the Philippine Tarsier Foundation in Bohol, where flash photography and touching are banned.
A very old lineage
Tarsiers belong to an ancient group of primates. Fossils of tarsier-like animals date back about 45 million years.
For a primate with a surprising defense, see is there a venomous primate.
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