drawing of a colugo
Colugo is the common name for any of the arboreal gliding mammals comprising the family Cynocephalidae and the order Dermoptera, characterized by a wide, fur-covered membrane that extends around their body, allowing them to glide. There are only two extant species known, Cynocephalus volans (Philippine colugo) of the Philippines and Galeopterus variegates (Sunda colugo, also C. variegates) of Southeast Asia. These two species, along with two extinct species (genus Dermotherium), make up the entire family and order (although some researchers have found support to further divide the Sunda colugo into three species).
Colugos also are known as cobegos or flying lemurs (Philippine flying lemur, Sunda flying lemur), although they are not true lemurs. They are the most capable of all gliding mammals, using the flaps of extra skin to glide from higher to lower locations.
Colugos provide ecological functions in terms of seed dispersal and as food for predators. In particular, C. volans is a very important prey animal for the endangered Philippine dagle, accounting for a large part of its diet. For humans, colugos sometimes serve as a meat and fur source, but also are important in adding to the diversity and wonder of nature, being able to glide very long distances between trees.
Extant colugos are fairly large for a tree-dwelling mammal. At about 35 to 40 centimeters (14 to 16 inches) in length and 1 or 2 kilograms (2 or 4 pounds) in weight, they are comparable to a medium-sized oppossum or a very large squirrel. They have moderately long, slender limbs of equal length front and rear, 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. When born, the colugo weighs only about 35 grams (1.2 ounces) and do not reach adult size for 2 to 3 years (Macdonald 2006).
The most distinctive feature of colugos, or flying lemurs, is the membrane of skin that extends between their limbs and gives them the ability to glide long distances between trees. Of all the gliding mammals, the colugos have the most extensive adaptation to flight. Their gliding membrane, or patagium, is as large as is geometrically possible: It runs from the shoulder blades to the fore-paw, from the tip of the rear-most finger to the tip of the toes, and from the hind legs to the tip of the tail (MacKinnon 1984). Unlike in other known gliding mammals, even the spaces between the fingers and toes are webbed to increase the total surface area, as in the wings of bats. As a result, colugos were traditionally considered being close to the ancestors of bats, but are now usually seen as the closest living relatives to primates.
Colugos are surprisingly clumsy climbers. Lacking opposable thumbs and not being especially strong, they proceed upwards in a series of slow hops, gripping onto the bark of trees with their small, sharp claws. They are as comfortable hanging underneath a branch as sitting on top of it. In the air, however, they are very capable, and can glide 70 meters (230 feet) from one tree to another with minimal loss of height. They have been known to transverse 136 meters (446 feet) in total (Janečka et al. 2008).
The extant colugos are shy, nocturnal, and restricted to the tropical rainforests of Southeast Asia. In consequence, remarkably little is known about their habits, although they are believed to be generally solitary, except for mothers nursing young. They are certainly herbivores, and are thought to eat mostly leaves, shoots, flowers, and sap, and probably fruit as well. They have well-developed stomachs and long intestines, capable of extracting nutriment from leaves.
The incisor teeth of colugos are highly distinctive; they are comb-like in shape, with up to twenty tines on each tooth. The second upper incisors have two roots, another unique feature among mammals (MacKinnon 1984). The function of these adaptations is not currently known. The dental formula of colugos is:
Although they are placental mammals, colugos are marsupial-like in their breeding habits. The young are born after just 60 days of gestation in a tiny and undeveloped form, and spend their first six months or so of life clinging to the mother's belly. To protect them and transport them she curls her tail up to fold the gliding membrane into a warm, secure quasi-pouch. Breeding is fairly slow as the young do not reach full size until they are two or three years old (MacKinnon 1984).
Classification and species
Two extant species are recognized, the Philippine flying lemur (Cynocephalus volans) and the Sunda flying lemur (Galeopterus variegatus). In addition, two extinct species are recognized, Dermotherium major and D. chimaera.
- ORDER DERMOPTERA
However, Janečka et al. (2008), examining genetic variation and morphological data for the broadly distributed Sunda colugo (Galeopterus variegatus) found evidence that two additional species should be recognized, elevating the Javan colugo and Bornean colugo from subspecies to species level.
It should also be noted that there are a number of synonyms that appear in the literature at the family, generic, and species level, and it is common in some taxonomies to place the two currently recognized species in the same genus of Cynocephalus (Stafford 2005a, 2005b, 2005c):
- Family Cynocephalidae. Synonyms are Colugidae, Galeopithecidae, and Galeopteridae.
- Genus Cynocephalus. Synonyms are Colugo, Dermopterus, Galeolemur, Galeopithecus, Galeopus, and 'Pleuropterus.
- Species Galeopterus variegates. Synonyms are Cynocephalus variegatus, Galeopterus temminckii, Cynocephalus variegatus, Galeopterus gracilis, and many others.
- Species Cynocephalus volans. Synonyms are C. philippinensis and C. philippensis.
The Sunda colugo, also known as the Sunda flying lemur (Galeopterus variegatus) and Malayan flying lemur, is found in Southeast Asia, in the countries of Brunei Darussalam, Cambodia, Indonesia (Sumatra, western Java, and Kalimantan), Lao People's Democratic Republic, Malaysia, Myanmar, Singapore, Thailand, and Vietname (Boeadi and Steinmetz 2008). It is strictly arboreal, forest dependent, and found in evergreen forest below 1000 meters, generally sleeping in coconut trees during the day and feeding on young fruits during the night (Boeadi and Steinmetz 2008). After a 60-day gestation period, a single offspring is carried on the mother's abdomen held by a large skin membrane (Burnie and Wilson 2005).
Often the species name is given as Cynocephalus variegatus. As noted above, Janečka et al. (2008) found genetic and morphological evidence that two additional species should be recognized, elevating the Javan colugo and Bornean colugo subspecies, thus delineating three species of the Sunda colugo.
The Philippine colugo or Philippine flying lemur is endemic to the Philippines, found only in the Mindanao Faunal Region, where it has been recorded in a large number of islands. The species is widespread and has a presumed large population. It is common in lowland primary forest and secondary forest and in mixed forest and orchard areas, and can tolerate disturbed habitat (Gonzalez et al. 2008).
Evolutionary history and relationships
The Mixodectidae appear to be fossil Dermoptera. However although other Paleogene mammals have been interpreted as related to Dermopterans, the evidence for this is uncertain and many of them are no longer interpreted as being gliding mammals. At present, the fossil record of definitive dermopterans is limited to two species of the Eocene and Oligocene cynocephalid genus Dermotherium (Marivaux et al. 2006).
Recent molecular phylogenetic studies have demonstrated that colugos belong to the clade Euarchonta along with the treeshrews (order Scandentia) and the primates. In this taxonomy, the Euarchonta are sister to the Glires (lagomorphs and rodents), and the two groups are combined into the clade Euarchontoglires (Janecka et al. 2007).
Both species are listed as Least Concern on the IUCN list (Boeadi and Steinmetz 2008; Gonzalez et al. 2008). However, Galeopterus variegatus probably is declining in numbers, albeit not fast enough to be listed in any category other than Least Concern (Boeadi and Steinmetz 2008). Although Cynocephalus volans is limited to the Philippines, it is found on many islands and also is not felt to be declining at the rate required to be placed in a threatened category (Gonzalez et al. 2008).
While these two species are listed a threatened, both are effected by habitat loss and are considered to be declining. Commercial logging is a threat to C. volans, although they seem to be able to persist in disturbed forest (Gonzalez et al. 2008). In Samar, they are persecuted because they are thought to be bad omens, and in Bohol they are hunted for their fur (Gonzalez et al. 2008). G. variegatus also is threatened by hunting and by competition with the plantain squirrel Callosciurus notatus (Boeadi and Steinmetz 2008). It is not hunted widely by local populations, given the lack of meat and fur, but there has been increased hunting pressure (Boeadi and Steinmetz 2008).
C. volans also is preyed upon by the gravely endangered Philippine Eagle: Some studies suggest that colugos account for 90 percent of the eagle's diet. It is not known how the diurnal eagles catch so many of the nocturnal colugos, which are thought to spend the greater part of the day curled up in tree hollows or hanging inconspicuously underneath a branch.
ReferencesISBN links support NWE through referral fees
- Boeadi, and R. Steinmetz. 2008. [http://www.iucnredlist.org/details/41502 Galeopterus variegatus. 2008 IUCN Red List of Threatened Species. Retrieved January 29, 2009.
- Burnie, D., and D. E. Wilson (eds.). 2005. Animal: The Definitive Visual Guide to the World's Wildlife. Dorling Kindersley. ISBN 0756616344.
- Gonzalez, J. C., C. Custodio, P. Carino, and R. Pamaong-Jose. 2008. Cynocephalus volans. 2008 IUCN Red List of Threatened Species. Retrieved January 29, 2009.
- Janečka, J. E., W. Miller, T. H. Pringle, F. Wiens, A. Zitzmann, K. M. Helgen, M. S. Springer, and W. J. Murphy. 2007. Molecular and genomic data identify the closest living relative of primates. Science 318 (5851): 792–794. PMID 17975064. Retrieved January 29, 2009.
- Janečka, J. E., K. M. Helgen, N. T.-L. Lim, M. Baba, M. Izawa, Boeadi, and W. J. Murphy. 2008. Evidence for multiple species of Sunda colugo. Current Biology 18(21): R1001-R1002. Retrieved January 29, 2009.
- Macdonald, D. W. (ed.). 2006. The Encyclopedia of Mammals. Oxford University Press. ISBN 0199206082.
- MacKinnon, K. 1984. Colugos. Pages 446-447 in D. Macdonald, The Encyclopedia of Mammals. New York: Facts on File. ISBN 0871968711.
- Marivaux, L., L. Bocat, Y. Chaimanee, J.-J. Jaeger, B. Marandat, P. Srisuk, P. Tafforeau, C. Yamee, and J.-L. Welcomme. 2006. Cynocephalid dermopterans from the Palaeogene of South Asia (Thailand, Myanmar and Pakistan): Systematic, evolutionary and palaeobiogeographic implications. Zoologica Scripta 35(4): 395–420. Retrieved January 29, 2009.
- Stafford, B. J. 2005a. Cynocephalidae. In D. E. Wilson and D. M. Reeder (eds.), Mammal Species of the World, 3rd edition. Johns Hopkins University Press. ISBN 0801882214.
- Stafford, B. J. 2005b. Cynocephalus volans. In D. E. Wilson and D. M. Reeder (eds.), Mammal Species of the World, 3rd edition. Johns Hopkins University Press. ISBN 0801882214.
- Stafford, B. J. 2005b. Galeopterus variegates. In D. E. Wilson and D. M. Reeder (eds.), Mammal Species of the World, 3rd edition. Johns Hopkins University Press. ISBN 0801882214.
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Marsupialia: | Paucituberculata (shrew opossums) | Didelphimorphia (opossums) | Microbiotheria | Notoryctemorphia (marsupial moles) | Dasyuromorphia (quolls and dunnarts) | Peramelemorphia (bilbies, bandicoots) | Diprotodontia (kangaroos and relatives)
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