Physical characteristics

Colugos are medium-sized arboreal mammals with very soft, dense fur. The pelage shows considerable variation in color, although the dorsal fur is typically brown in males and grayish brown in females. The color of the ventral fur varies

A Malayan colugo (Cynocephalus variegatus) with baby, in Malaysia. (Photo by Peter Ward. Bruce Coleman, Inc. Reproduced by permission.)

The gastrointestinal tract is very specialized as a reflection of the strictly herbivorous diet. Surprisingly, the stomach is relatively small and narrow, and there is an abbreviated small intestine, which is shorter than the colon. However, the caecum is greatly enlarged, providing a chamber for symbiotic bacteria that assist in digesting plant material. The dental formula is, giving a total of 34 teeth, and there are a number of dental peculiarities. All canine teeth and the posterior incisors in the upper jaw are double-rooted, an unusual feature otherwise found only in a few insectivores. In mammals generally, these teeth usually have only a single root. The first two incisors on either side of the lower jaw, which are tilted forwards (procumbent), are unique among mammals in that in each one the crown is notched and comblike, with up to 20 tines on each tooth. (There is a superficial resemblance here to the toothcomb found in lemurs and lorises among primates and in tree shrews, but in those mammals individual teeth form single tines of the "comb.") The function of the comblike lower incisors of colugos is unknown, although it has been suggested that they may be used in grooming the fur. It is highly likely that these special teeth are also used during feeding in some way. The molar teeth are relatively primitive, showing a simple three-cusped pattern in the upper jaw.

from yellow through bright orange to brownish red. The eyes are relatively large, reflecting adaptation for active movement at night, while the ears are small and almost naked. The snout is relatively long, giving the head a doglike appearance and accounting for the genus name Cynocephalus (literally "dog's head"). The skull is broad and relatively flat. The auditory bul-lae, which are also quite flat, are highly unusual among mammals both because of their bony composition and because the eardrum (tympanic membrane) is almost horizontal, a very primitive condition. The brain is also unusually small relative to body size and morphologically very primitive.

The most obvious gliding adaptation is a special membrane (patagium) extending around almost the entire margin of the body. All four limbs are relatively long and slender and the neck is long and mobile. During gliding, three dorsally furred membranes become stretched out on either side of the body: an anterior membrane (propatagium) between the side of the neck and the forelimb, an extensive lateral membrane (pla-giopatagium) between the forelimb and hindlimb, and a large posterior membrane (uropatagium) between the hindlimb and the tail. Other gliding mammals (certain rodents and marsupials) lack a uropatagium and have a long tail, whereas the tail is quite short in colugos. Furthermore, the patagium in colu-gos extends between the fingers and toes, such that the term "mitten-gliders" has been used. In contrast to bats, the colugo's membranes are not used for actual flight but merely for gliding, so there is always some loss of height during aerial movement between trees. Some degree of steering is achieved by altering the positions of the limbs and tail. The fingers and toes bear prominent, strongly curving claws that are used to cling to trees.

A Malayan colugo (Cynocephalus variegatus) in Tawau Hills Park, Sabah, Malaysia. (Photo by © Fletcher & Baylis/Photo Researchers, Inc. Reproduced by permission.)

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