Known as the “world’s smallest monkey” because of its similarity in appearance to that primate, tarsiers, along with lemurs, tree shrews, and lorises, actually are members of a more primitive suborder of Prosimii or prosimian. They are amongst the oldest land species that have existed continuously in the Philippines, dating from the early Eocene period, 45 million years ago. The Philippine tarsier has various distinctive habits and characteristics that make it an object of both popular curiosity and scientific research.
The Philippine tarsier has thin, rough fur which is colored gray to dark brown. The narrow tail, usually used for balance, is bald except for a tuft of hair at the end and is about twice the body length. Its elongated "tarsus", or ankle bone, which gives the tarsier its name, allows it to jump at least 3 m from tree to tree. Its long digits are tipped with rounded pads that allow the tarsier to cling easily to trees and grip almost any surface. The thumb is not truly opposable, but the first toe is. All of the digits have flattened nails, except for the second and third toes, which have sharp claws specialized for grooming. Like all tarsiers, the Philippine tarsier's eyes are fixed in its skull; they cannot move in their sockets. Instead, a special adaptation in the neck allows its round head to be rotated 180°. Their eyes are disproportionately large, having the largest eye-to-body weight ratio of all mammals. These huge eyes provide this nocturnal animal with excellent night vision. In bright light, the tarsier's eyes can constrict until the pupil appears to be only a thin spot. In low light or darkness, the pupil can dilate and fill up almost the entire eye. The large membranous ears are mobile, appearing to be almost constantly moving, allowing the tarsier to hear any movement.
This species is native to the Philippines, where it lives on the islands of Leyte, Samar, Dinagat, Siargao, Bohol, Mindanao, Basilan, and Maripipi. Philippine tarsiers inhabit areas of tall grasses, bamboo shoots, small trees, and bushes in tropical rainforests. They prefer the jungle canopy and leap from limb to limb.
Philippine tarsiers are nocturnal but are also active at dawn and dusk. During the day they sleep in dense vegetation or sometimes in a hollow tree. At sunset, they begin searching for insect prey. They are agile acrobats, easily leaping vertically from tree to tree. Philippine tarsiers are solitary but may sometimes associate in groups of four animals or fewer. They demonstrate little fear of other species and especially humans unless a quick movement is made. When they are threatened they make a high-pitched squeak. Although less vocal than other primates, a tarsier uses a variety of means of communication, including calls for territorial maintenance and the spacing of males and females. They also use scent marks from glandular secretions to delineate their territories.
Philippine tarsiers are carnivores (insectivores). They mainly consume insects but will also eat spiders, lizards, birds, and other small vertebrates.
Philippine tarsiers are monogamous, which means that one male mates with one female exclusively. They tend to breed at any time of the year. A single baby is born following a gestation period of about six months. A baby tarsier is very well developed when born, with a full covering of fur and open eyes, and after just one day it is able to climb. As a mother climbs around the trees, her young will cling to her belly or is carried in her mouth. When 42-60 days old, Philippine tarsiers start to hunt their own insects, and soon after, they are weaned. They usually reach sexual maturity between the age of one and two years.
Tarsiers are under severe threat by trappers and hunters, who shake them out of the trees or chop off the branches of trees where they live. They are also popular as pets, especially in Mexico. However, tarsiers do not often live long in captivity, as being captured traumatizes them so much that they will beat their head against the cage, to the point of killing themselves. These animals are also significantly affected by the increasing deforestation of their native habitat.
According to Primate GCAP Report, the total population size of the Philippine tarsier is less than 2,500 individuals, including 700 tarsiers in Bohol’s Forest. Currently, this species is classified on the IUCN Red List as near threatened (NT) and its numbers continue to decrease.
Being predators, Philippine tarsiers may help to structure insect communities. To the extent that they are preyed upon by other animals, they may impact predator populations.
