The Philippine tarsier, (Tarsius syrichta) is very peculiar small animal. In fact it is one of the smallest known primates, no larger than a adult men’s hand. Mostly active at night, it lives on a diet of insects. Folk traditions sometimes has it that tarsiers eat charcoal, but actually they retrieve the insects from (sometimes burned) wood. It can be found in the islands of Samar, Leyte, Bohol, and Mindanao in the Philippines.
If no action is taken, the tarsier might not survive. Although it is a protected species, and the practice of catching them and then selling them as stuffed tarsiers to tourists has stopped, the species is still threatened by the destruction of his natural forest habitat. Many years of both legal and illegal logging and slash-and-burn agriculture have greatly reduced these forests, and reduced the tarsier population to a dangerously small size. If no action is taken now, the Philippine tarsier can soon be added to the list of extinct species.
Eyes. In comparison with his body size, the eyes of the tarsier are enormous. In volume, the capacity of the bony eye orbits, or eye sockets, is larger than that of the brain case, and also larger than its stomach. Their eye sockets have post-orbital closure rather than the postorbital bar of the prosimians. This feature keeps the eyeballs from being pressed against by the powerful temporal muscles to their sides.
Tail. The tarsier has a relatively very long tail (232 mm), generally naked except for a tuft of hair at its end. The underside has dermal ridges like those found on human hands and feet. Its tail is used for balancing like a tripod; they prefer an erect posture at all times.
Head. Like an owl, the tarsier has a joint between its skull base and spine to allow head movement of a 180-degree arc. Its upper lip lacks a cleft yet, but still has muscles, so that it can make facial expressions. The adult brain weighs about 4 grams.
Teeth. Tarsiers have sharp teeth, enabling them to catch their prey easier. Unique among primates, tarsiers have only two, rather than four, incisors in their lower jaw. Their dental formula is 18.104.22.168 22.214.171.124 x 2 = 34.
Ankle bones. The name “tarsier” or “tarsius” is derived from the animal’s very long ankle bones. The tibia and fibula of the tarsiers are fused in their lower portions, acting as a shock absorber. This is considered a primitive trait, which can normally be seen in quadrupeds. The lower limbs are twice the length of its trunk. These enable the tarsier to leap about three meters from tree to tree. Its movements are similar to that of a frog.
Comparison with other Primates. Tarsiers share some characteristics with both the prosimians and the anthropoids, while they also have some characteristics peculiar to themselves. Taxonomists have classified them as intermediate between both groups and have assigned them to their own infraorder, which contains just one living genus: Tarsius. Fossil records of this genus are found, dating back to the Eocene epoch, from 54 to 36 million years ago.
Like many prosimians, they are nocturnal and have grooming claws and bicornuate uterus.
Like anthropoids, they do not have a tapetum (a reflective layer in their eyes).
In tarsiers, the internal structures of the nose and ears and the blood supply to the brain and to a developing fetus are more like those of monkeys than of lorises. The monthly sexual swellings of female tarsiers are also similar to those in anthropoids.