Colugos are medium-sized, arboreal mammals with a fur-covered membrane known as the patagium. It extends from their face to the tips of their claws and tail, similar to bats, an adaptive feature that is key to their arboreal lifestyle. Currently, there are only two living species: the Philippine flying lemur (Cynocephalus volans) and the Sunda flying lemur (Galeopterus variegatus), both belonging to the family Cynocephalidae and order Dermoptera. Although the two species are commonly referred to as flying lemurs, they are neither true lemurs nor are they capable of flying.
Their webbed fingers and toes make them highly efficient gliders, allowing them to cover long distances. Native to Southeast Asia, these mammals are found in the Philippines, Vietnam, Laos, Cambodia, Thailand, Myanmar, Malaysia, and Indonesia.
They are about 14 to 16 in (35 to 40 cm) long and weigh around 2.2 to 4.4 lb (1 to 2 kg).
Colugos have long, slender limbs and a medium-length tail covered by a membranous patagium that extends from the shoulder blades to the forepaws, stretches from the outermost fingers to the toes, and connects the hind legs to the tip of the tail.
Their webbed fingers and toes, with claw-like tips, provide a strong grip, while the soles of their feet act like suction cups to help them cling to tree trunks. Although their bones aren’t as light as a bat’s, they still aid in smooth gliding. Despite having a small head, colugos have large, forward-facing eyes for excellent night vision and small, rounded ears.
The Philippine flying lemur is smaller than the Sunda flying lemur, and its fur is darker and less spotted. However, the limbs of both species are approximately of the same length.
The skull is broad and flat, with distinct postorbital processes forming the eye sockets. Both the palate and the tympanic bullae are flat.
Teeth
Their teeth (34 in number), resembling those of carnivores, are relatively small, with the incisors shaped like tiny combs comprising up to 20 spikes on each tooth. The first upper incisors are reduced, while the second resembles canines and possesses two roots, a feature unique among mammals. The molars are tribosphenic (three cusps), with well-developed ridges called lophs for chewing coarse plant matter.
Their dental formula is 2.1.2.3/3.1.2.3.
The two extant species of colugos, the Philippine flying lemur or Philippine colugo and the Sunda flying lemur or Malayan colugo, fall under the only extant family, Cynocephalidae. The family derives its name from the Greek words kyōn, meaning dog, and kephalē, meaning head, referring to their broad heads with short snouts like those of a dog’s.
Molecular phylogenetic studies suggest that colugos have emerged as a basal group under the mirorder Primatomorpha. They were initially considered close relatives of treeshrews (order Scandentia) but are now thought to be most closely related to primates (order Primates), like lorises, pottos, and galagos, together called lorisoids.
It is believed that the ancestors of colugos split from other mammalian groups around 80 million years ago. Currently, the only definitive fossils of colugos are those of two species of the genus Dermotherium from the Eocene and Oligocene Epochs.
It is believed that, through the evolutionary process, these mammals became nocturnal and eventually developed night vision.
Colugos are exclusively native to the tropical forests of Southeast Asia. While the Philippine flying lemur, as their name suggests, inhabits the islands of the Philippines (including Bohol, Samar, and Mindanao), the Sunda flying lemur extends across Vietnam, Laos, Cambodia, Thailand, Myanmar, Malaysia, and Indonesia.
They are herbivorous and mostly feed on leaves, shoots, flowers, sap, and fruits.
Colugos are nocturnal and thus forage only at night, traveling as much as 1.7 km. They usually rest during the day, clasping high tree trunks or hiding in tree holes.
Although they cannot fly, they are excellent gliders, capable of covering impressive distances between trees. By stretching out their limbs and expanding their patagium (a membrane of skin), they increase their surface area, allowing for greater lift. This helps them stay in the air for longer periods.
Clinging to the tree bark with their claws, these mammals hop slowly and hang upside down when traveling along branches. Generally, they cover as much as 230 ft (70 m) without losing altitude. A Malayan colugo has been reported traveling about 490 ft (150 m) in a single glide.
Despite such long-distance traveling, they lack opposable thumbs and are clumsy climbers.
When a predator confronts a colugo, it either freezes completely and tries to camouflage itself against the surroundings or quickly glides away through the air to a nearby tree.
These mammals pick insects from trees and sometimes lick their bark for minerals and sap. Their specialized long intestines then extract nutrients from these difficult-to-digest fibrous plant materials, followed by a large sac-like cecum, where a number of beneficial microbes help break cellulose into simpler, easily digestible forms.
They can survive up to 15 years in captivity, but their lifespan in the wild is still unknown.
They typically mate throughout the year, with a gestation period of about two months for the Sunda flying lemur and around 105 days for the Philippine flying lemur. Both species usually give birth to a single infant, though twins are occasionally born. The newborns are underdeveloped and weigh only about 1.2 oz (35 g).
Despite being placentals, colugo mothers raise their babies like marsupials. The young cling to the mother’s belly till they are about six months old, after which they are weaned. The mother curls her tail and folds her patagium to form a pouch-like structure to keep her baby warm and secure.
The young attain sexual maturity at around two to three years.
They are preyed upon by snakes, like pythons, and birds, such as the Philippine Eagle, yellow-throated martens, long-tailed macaques, and owls. However, their main threat is humans, who often hunt them for meat and fur.
In 1996, the IUCN Red List classified the two colugo species as Vulnerable (VU). By 2008, they were downlisted to Least Concern (LC). However, they are still threatened by habitat destruction and fragmentation. Locals hunting them pose a secondary threat to their populations.
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