Tarsiers are any haplorrhine primates of the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all its species living today are found in the islands of Southeast Asia.
Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 millimetres (0.63 in) in diameter and is as large as, or in some cases larger than, its entire brain.[15][16] The unique cranial anatomy of the tarsier results from the need to balance their large eyes and heavy head so they are able to wait silently for nutritious prey.[17] Tarsiers have a strong auditory sense, and their auditory cortex is distinct.[17] Tarsiers also have long hind limbs, owing mostly to the elongated tarsusbones of the feet, from which the animals get their name. The combination of their elongated tarsi and fused tibiofibulae makes them morphologically specialized for vertical clinging and leaping.[18] The head and body range from 10 to 15 cm in length, but the hind limbs are about twice this long (including the feet), and they also have a slender tail from 20 to 25 cm long. Their fingers are also elongated, with the third finger being about the same length as the upper arm. Most of the digits have nails, but the second and third toes of the hind feet bear claws instead, which are used for grooming. Tarsiers have soft, velvety fur, which is generally buff, beige, or ochre in color.[19]
Philippine tarsiers are capable of hearing frequencies as high as 91 kHz. They are also capable of vocalizations with a dominant frequency of 70 kHz.[22]