Sunda Colugo

Source: Wikimedia Commons

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Dermoptera

Family: Cynocephaildae

Genus: Galeopterus

Species: G. variegatus

The Sunda Colugo or Galeopterus variegates, is often given the common name flying lemur. However the Sunda Colugo is not a lemur at all but rather a species of colugo.  They are not closely related to the true lemur, found in Madagascar, but instead are classified in the order, Dermoptera. Dermoptera as well as Scandentia and Chiroptera are found to be the closest living relatives of Primates (5). The word Dermoptera comes from the Greek words derma and ptera; derma means skin while ptera means wing, thus skin-wing (2). There are only two species of colugo the Philippine Colugo, Cynocephalus volans, and the Sunda Colugo. The Philippine Colugo is found in the southern Philippines while the Sunda Colugo is found in Southeast Asia. 

Range and Habitat

Source: Wikimedia Commons

           
The Sunda flying lemur is found in Southeast Asia and is endemic, native or restrictive, to Indochina and Sundaland. This area is made up of the Malay Peninsula and the vast islands of Borneo, Sumatra, and Java. These flying lemurs can also be found on several of the surrounding smaller islands (1)(5). The Sunda flying lemur is arboreal meaning it spends its’ entire life in the tops of trees located in lowland tropical rain forests (1). They can also be found in gardens, secondary forests, mountainous areas, rubber and coconut plantations, and mangroves. The diverse habitats in which a Sunda flying lemur can live, lead to the possibility of the presence of one in a multitude of areas including rural ones (6). This species is very versatile, allowing it to adapt to forests that face human destruction, however the disturbed forests do encourage some to live in plantations. 

Physical Description

Source: Batconsultancy

Sunda flying lemurs have relatively small heads compared to their bodies with large forward-facing eye, processing excellent binocular vision, wide brows, and small round ears. Their snouts are short and blunt with no obvious whiskers on their face. The flying lemurs’ fur is tightly packed making it very dense and appears marbled. The underside of the fur is light in color while the dorsal fur varies in the following colors; white, gray, black, and red (1). Their dorsal marbled fur often has vivid colored markings that resemble lichens on trees, which help them stay camouflaged, in their surroundings. The Sunda Colugo is unable to fly, however they have a thin film of skin known as the patagium, which enables them to glide. The patagium is completely covered in fur and extends along both the upper and lower extremities to the neck and tail. When the Sunda Colugo glides the patagium may extend to a width of 0.7 meters, with the assistance of their extensor muscle, located inside of the flank tissue (1). The flying lemur is a quadruped having all its' legs almost identical in size and posing a membrane between its digits making them webbed. It’s feet include flattened digits, allowing the soles or its’ feet to form sucking discs, aiding them in tree climbing. The flying lemur weigh any where from 0.9 kg to 2 kg and is about 0.33 to 0.42 meters in length, having a tail 0.17 to 0.27 meters in length, making up more than half of their body length (1). The dentition of the flying lemur aids in its ability to consume its food of choice. It has 34 carnivore-like teeth; its bottom incisors are a unique comb-shape, exclusive to the family Cynocephalidae. These comb-shaped teeth are thought to assist in straining food and grooming. The second incisors of the Sunda flying lemur contain two roots unlike most incisors of mammals, which possess only a single root. The flying lemurs' front upper jaw is absent of teeth, containing incisors only in the sides of its' jaw (1). Their canines resemble premolars proving evidence that these flying lemurs are indeed herbivores. 

Behavior

The Sunda flying lemur is mainly nocturnal. During the day they can be found sleeping in holes in coconut trees or high in the dense foliage of treetops (1). When perching in a tree these flying lemurs grasp the underside of branches or the trunk with all four limbs. They are usually seen perching against a tree with their head pointing upward (2). They go about climbing trees by stretching their two front legs forward and then bringing the back legs in to meet the front, giving them a hopping appearance. When threatened they either climb higher into the tree or completely stop moving, making them relatively easy to catch. These flying lemurs are strictly arboreal and quite helpless on the forest floor. Although they are not nimble on the forest floor they are able to glide over 100 meters with little loss in elevation (1). Gliding is done in a steady controlled manner landing with their heads up neatly and precisely (2). These animals often live alone or in small loosely connected groups. Sleeping and feeding areas are the only known areas that they may become territorial of. The Sunda flying lemur is strictly herbivorous, feeding on soft plant parts. These soft plant parts include: fruit, flowers, buds, young leaves, nectar, and sap (1). These lemurs have advanced stomachs and long intestines, allowing them to extract nutriment from hard roughage (3). Their comb-shaped incisors help to scrape up the sap from trees and to strain fruits and flowers (1). As eutherians, colugos give birth to live young however their gestation period is shorter, similar to marsupials. Their young are born after a 60-day gestation period in a small undeveloped form; spending the first six months grasping its' mother’s abdomen (3). The mother folds her gliding membrane by curling her tail towards her stomach to fold a warm, safe temporary pouch, for protection and transport. Breeding in this species is a rather slow process. The young do not reach their full mature size until they are about two to three years of age (3).

Physiology/Evolutionary History

The Sunda flying lemur is a nocturnal animal that is one of the closest living relatives to primates. It was thought that a nocturnal activity pattern was fundamental to the adaptive origins of primates. However with recent research, on the basis of being able to differentiate between the opsin genes of various nocturnal primates, this view has been altered. A resemblance was found between the opsin genes and the activity patterns of several species. These species include members of following orders: Primates, Dermoptera, and Scandentia. Sunda Colugo's possess complete short wavelength sensitive (S-) opsin genes and long wavelength sensitive (L-) opsin genes that are both complete and with out damage (7). These opsin genes are both expressed within cone photoreceptors located in the retina. It was thought that since colugus are mostly nocturnal and have been around for 45 million years that they may have a disabled S-opsin gene. However, this is not the case for the Sunda colugos, expressing both the S- and L-opsin genes. Characteristics that are normally consistent with the  selection in exon 1 of the S-opsin in the Sunda Colugo were also found. With this knowledge of the S- and L-opsin genes being fully functioning in a nocturnal animal, it is disproved that the S-opsin gene will under go mutations when an animal is nocturnal. The evolutionary history of nocturnal primates with completely functioning S-opsin genes evolving from a diurnal ancestor are also challenged. (7). Colugos, having the presence of fully functioning S-cones could aid it the enhancement contract under twilight conditions. These findings suggest that colugos are paving the path of understanding both the ecology and evolution of many nocturnal animal and their color vision (7). 

Conservation Status
The IUCN categorized the Sunda Colugo as Least Concern (4), however other sources consider this species as near threatened (6). The population of the flying lemur is decreasing. Due to this decrease they are now protected by national legislation, one of these protected areas include Peninsular Malaysia, containing several flying lemurs (4). An estimated population was given for a protected forest in Singapore. The estimated amount was about one animals per five acres, yielding an estimated number of Sunda Colugos to be 1000 individuals across Sigapore’s 5,000 acres of protected forest (5).The main reason for this population decline is thought to be due to habitat loss. Deforestation takes away the Sunda flying lemur’s natural habitat. These flying lemurs are dependent on trees for survival, due to their gliding locomotion and inability to move quickly on the forest floor. There is also possible competition with the plantain squirrel, Callosciurus notatus that could be leading to the population decline (3). The last cause of the population decline in the flying lemur is the increased pressure every year by the Baduy Tribe. The Sunda flying lemur is hunted traditionally by the local people for consumption and fur (4).    

References

   (1) Beatson, K. (2011, January 1). Galeopterus variegates. Retrieved November 23, 2014, from http://animaldiversity.ummz.umich.edu/accounts/Galeopterus_variegates/ 

   (2) Malayan Colugo Cynocephalus variegatus. (2006, January 8). Retrieved November 23, 2014, from http://www.wildsingapore.per.sg/discovery/factsheet/colugo.htm

   (3) Sharp, A., Burdon, R., & Harrison, N. (n.d.). Colugo (Galeopterus variegatus). Retrieved November 23, 2014, from http://www.safeproject.net/animal-sightings/colugo-galeopterus-variegatus/

   (4) Steinmetz, R., & Boeadi, R. (2008, January 1). Galeopterus variegatus. Retrieved November 23, 2014, from http://www.iucnredlist.org/details/41502/0

   (5) Sunda Flying Lemur (Galeopterus variegatus) - Information on Sunda Flying Lemur - Encyclopedia of Life. (n.d.). Retrieved November 24, 2014, from http://eol.org/pages/1040858/overview

   (6) Nasir, M. D. M., & Abdullah, M. T. (2010). Distribution of the Sunda Colugo (Galeopterus variegatus) in Malaysia (Peninsular, Sabah, Sarawak). Tropical Life Sciences Research, 21(2), 69–83. Retrieved November 23, 2014, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3819077/

   (7) Moritz, G., Lim, N., Neitz, M., Peichl, L., & Dominy, N. (2013). Expression and Evolution of Short Wavelength Sensitive Opsins in Colugos: A Nocturnal Lineage That Informs Debate on Primate Origins. Evolutionary Biology. Retrieved November 23, 2014, from http://link.springer.com/article/10.1007/s11692-013-9230-y/fulltext.html