Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 mm in diameter and is as large as its entire brain. 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.Tarsiers have an incredibly strong auditory sense because their auditory cortex is very distinct. Tarsiers also have very long hind limbs, due mostly to the extremely elongated tarsus bones 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. 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 very soft, velvety fur, which is generally buff, beige, or ochre in color.