Each tarsier eyeball can be as big as its entire brain
A tarsier's eyes are about 16 millimetres across, each as large as its brain or larger. Since the eyes cannot swivel, the tiny primate turns its head 180 degrees each way to see all around. It is also the only living primate that eats nothing but animals.
Tarsiers are small haplorhine primates now found only on islands of Maritime Southeast Asia, including Brunei, Indonesia, Malaysia and the Philippines, typically in forests with lianas that help them climb. Fossils show the group once ranged more widely across Asia, and their teeth have changed little except in size for about 45 million years. The genus Tarsius has a longer fossil history than any other primate genus, though assigning the oldest fossils to it is doubtful.
The name comes from their stretched tarsal bones. With a body of 10 to 15 centimetres, hind limbs about twice as long and a slender tail of 20 to 25 centimetres, they are built for clinging to vertical stems and leaping. Unlike most night animals, they lack a reflective layer behind the retina. Philippine tarsiers hear frequencies up to 91 kilohertz and call at around 70, far above human hearing. The wiring between their eyes and brain differs from all other primates, which some neuroscientists take as a sign of a very early, separate lineage.
They hunt by pouncing on insects, spiders and other invertebrates, and sometimes take lizards, small frogs, tree-climbing crabs or even baby bats. Shy and easily stressed by light and noise, they still mob predators: one warning call can summon two to ten tarsiers, mostly males from several territories, to harass a snake or cat. Females carry a single young for about six months, born furred and able to climb within a day.
Classification has been reshuffled repeatedly. In 2010 Colin Groves and Myron Shekelle proposed three genera, Philippine, western and eastern tarsiers, and genetic work in 2014 found hidden diversity on Mindanao. Tarsiers have never bred successfully in captivity; a sanctuary near Corella on Bohol, founded by Carlito Pizarras, lets visitors watch them in semi-wild conditions. The Siau Island tarsier is critically endangered.
Source: Tarsier
