Tarsiers are prosimians, or primitive primates, in the family Tarsiidae, found the islands of Southeast Asia. Tarsiers have only 34 teeth, unlike their closest prosimian relatives, the lemurs and lorises, which have 36 teeth. Also, the upper lip of tarsiers is not fastened to the gum underneath, so that the face can be mobile, rather like the more advanced primates, monkeys and apes. Tarsiers are the only prosimians with a nose that does not stay moist. A moist nose usually indicates that a mammal depends heavily on its sense of smell.
Tarsiers are often called "living fossils" because they most resemble fossil primates from about 40 million years ago. Thus, instead of being grouped with other prosimians, tarsiers are placed in a separate order, the Tarsioidea.
The head and body of the tarsier measure about 5 in (12.5 cm) in length, and its long, thin, naked tail is an additional 8 or 9 in (20-22 cm). Their average weight is only slightly over 4 oz (114 g). Tarsiers have soft, brown, olive, or buff fur on their head and back, which is a lighter buff or gray below. The tail may have a small puff of fur on the end. Both the second and third toes of the hind feet have toilet claws, which are long claws used for grooming and digging for insects. When grooming, tarsiers make a foot fist, from which these claws protrude.
Moving somewhat like a small, furry frog, a tarsier can leap from small branch to small branch. In order to do this efficiently, the tibia and the fibula (the two lower leg bones) are fused about halfway down their length, giving the leg more strength. Tarsiers also have elongated ankle bones, which helps them leap, and which gives them their name, tarsier, a reference to the tarsal, or ankle, region. The legs are much longer than their arms.
These curious little nocturnal creatures dart around the undergrowth and low trees, keeping out the realm of the larger animals until they want to leap across the ground to gather up prey. Tarsiers are carnivorous, eating insects and small lizards. They have fat pads on the tips of their thin fingers and toes that help them cling to trees. These primates probably do not build nests.
Tarsiers have large bulging eyes, which close quickly for protection if large insect prey comes near. The eyes also face forward, providing binocular vision, an aid in catching insects at night. The animal's large ears can also be folded for protection. Their eyes do not move in their head, but they can turn their heads in a full half circle, like an owl. This fact accounts for the belief, recorded in Borneo, that tarsiers have detachable heads. The brain of some tarsier species weighs less than a single eye. Their big ears constantly move, listening for sounds of danger.
Tarsiers form family groups consisting of the male, the female, and their young. Each family stays in its own territory, and fusses loudly if another tarsier enters it. After a 180-day gestation, the female produces a single, fairly mature infant. The offspring rides either under its mother's abdomen or in her mouth. When she is off hunting, she may leave it in a safe place. The young can hunt on its own by the age of one month old, when it is also ready to leap.
There are only three species of tarsier in a single genus, Tarsius. All are endangered to some degree, and their ranges do not overlap.
The Mindanao or Philippine tarsier (T. syrichta) lives on several Philippine islands, where its forest habitat is being destroyed. The Western, or Horsfield's tarsier, T. bancanus, lives on Sumatra, Borneo, Java, and the nearby islands, and has been protected in Indonesia since 1931. The middle finger of its hand is amazingly long, almost as long as its upper arm.
The spectral, eastern, or Sulawesi tarsier (T. spectrum), lives in three areas of Sulawesi (formerly Celebes) and nearby islands. Unlike the other species, the spectral tarsier has scales on a skinny tail, rather like a mouse. There is the possibility that another species, T. pumilus, still exists in the mountains of central Celebes.
Over the years, many attempts have been made to domesticate tarsiers. However, without a continuous source of live food, these primates quickly die.
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Jean F. Blashfield