Colugos (/kəˈluːɡoʊ/)[2][3] are arboreal gliding mammals that are native to Southeast Asia. Their closest evolutionary relatives are primates. There are just two living species of colugos: the Sunda flying lemur (Galeopterus variegatus) and the Philippine flying lemur (Cynocephalus volans). These two species make up the entire family Cynocephalidae (/ˌsaɪnoʊˌsɛfəˈlaɪdi, -ˌkɛ-/)[4] and order Dermoptera (not to be confused with Dermaptera, an order of insects known as earwigs).[1][5]
They reach lengths of 35 to 40 cm (14 to 16 in) and weigh 1 to 2 kg (2.2 to 4.4 lb).[6] They have long, slender front and rear limbs, a medium-length tail, and a relatively light build. The head is small, with large, front-focused eyes for excellent binocular vision, and small rounded ears.
The incisor teeth of colugos are highly distinctive; they are comb-like in shape with up to 20 tines on each tooth. The incisors are analogous in appearance and function to the incisor suite in strepsirrhines, which is used for grooming. The second upper incisors have two roots, another unique feature among mammals.[7] The dental formula of colugos is: 2.1.2.33.1.2.3
Colugos are proficient gliders, and they can travel as far as 70 m (230 ft) from one tree to another without losing much altitude,[8] with a Malayan colugo (Galeopterus variegatus) individual having travelled about 150 m (490 ft) in one glide.[9]
Of all the gliding mammals, colugos have the most perfected adaptation for flight. They have a large membrane of skin that extends between their paired limbs and gives them the ability to glide significant distances between trees. This gliding membrane, or patagium, runs from the shoulder blades to the fore paws, from the tip of the rear-most fingers to the tip of the toes, and from the hind legs to the tip of the tail.[7] The spaces between the colugo's fingers and toes are webbed. As a result, colugos were once considered to be close relatives of bats. Today, on account of genetic data, they are considered to be more closely related to primates.[10]
Colugos are unskilled climbers; they lack opposable thumbs.[11] They progress up trees in a series of slow hops, gripping onto the bark with their small, sharp claws. They spend most of the day resting. At night, colugos spend most of their time up in the trees foraging, with gliding being used to either find another foraging tree or to find possible mates and protect territory.[12]