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Dremomys rufigenisAsian red-cheeked squirrel

By Yuka Sugiura

Geographic Range

Red-cheeked squirrels (Dremomys rufigenis) occur in southern China and northeastern South Asia, to the west of the Indian subcontinent, and to the western Indochinese Peninsula and the northern-to-middle Malay Peninsula. They are found in many protected areas in Southeast Asia. (Can, et al., 2008; Duckworth, 2017; Francis, 2008; Nowak, 1999; Smith and Xie, 2008; Timmins and Duckworth, 2008)

Habitat

Red-cheeked squirrels are a half-terrestrial and half-arboreal species that are found in low and high elevations, with an upper limit of 1,500 m. They live in tropical evergreen forests and shrublands. They are most active between the ground and about four feet off the ground. They have been observed to go up to the forest canopy to eat ripe fruit. They are also found in degraded and fragmented habitats. (Duckworth, 2017; Duckworth, et al., 1999; Koyabu, et al., 2009; Nowak, 1999)

  • Range elevation
    1500 (high) m
    4921.26 (high) ft

Physical Description

There is limited available information on body masses and body lengths of red-cheeked squirrels. According to a study by Koyabu et al. (2012), the mean body weight of wild adult red-cheeked squirrels sampled in Vietnam (n = 11) was 221 g. According to Hayssen (2008b), the body mass of any squirrel can be predicted from body length using this equation: log10 body mass = −4.30 + 2.91(log10 body length) − 0.07(Pteromyini) (1 is substituted for Pteromyini when the animals is a flying squirrel and 0 if it is not). When the mean body weight of 221 g is fitted to this equation (Pteromyini = 0), the body length is estimated to be 192 mm. Red-cheeked squirrels have a grey brown body color. They have long necks, which are thought to help them search for insects and invertebrates on the ground. Their long splanchnocranium, a portion of a skull that comprises the mandibular, hyoid, and gill arches, helps insectivorous foraging behaviors on land. It is described that the skull sizes of populations in Malaysia are larger than those of the populations in Vietnam, Laos and Thailand. Species in the genus Dremomys typically have elongated rostra and short bushy tails. (Corbet and Hill, 1992; Endo, et al., 2003; Koyabu, et al., 2012)

  • Average mass
    221 g
    7.79 oz
  • Average length
    192 mm
    7.56 in

Reproduction

There is little available information on reproduction in red-cheeked squirrels. It is known that the mating system of squirrels (Family Sciuridae) is polygynandrous; both males and females mate with multiple partners during a single breeding season. Therefore, a single litter usually has young from multiple fathers. (Thorington and Ferrell, 2006)

There is little available information on general reproductive behavior in red-cheeked squirrels. For squirrels in general, sexual maturity occurs when males develop their testes females enter estrus. Males typically chase females to mate during the breeding season. Litter sizes of two species in the same genus as red-cheeked squirrels were reported by Hayssen (2008ab); litter sizes for orange-bellied Himalayan squirrels (Dremomys lokriah) averaged 3.67, while litter sizes for Perny's long-nosed squirrels (Dremomys pernyi) average 4.00. (Hayssen, 2008a; Hayssen, 2008b; Thorington and Ferrell, 2006)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Breeding interval
    unknown
  • Breeding season
    unknown

There is little available information on parental care in red-cheeked squirrels. It is known that all squirrels give birth to litters in a nest and they are born altricial. Therefore, female parental care of the young, such as lactating and providing food is important. Also, squirrels are polygynandrous, so males cannot confirm whether offspring are theirs or not. Therefore, parental care by males is not very likely. (Davies, et al., 2012; Thorington and Ferrell, 2006)

Lifespan/Longevity

The lifespan of red-cheeked squirrels is about four years. (Duckworth, 2017)

  • Average lifespan
    Status: wild
    4 years

Behavior

Red-cheeked squirrels are diurnal. They are active both on the ground and in trees, and are most active at heights below four feet. Little has been investigated about the behavior of this species or this genus, but tree squirrels are known to be generally solitary, unlike ground squirrels. Also, tree squirrels are very agile when moving among trees. Squirrels in general are known to be territorial. (Brown, et al., 2014; Duckworth, 2017; Thorington and Ferrell, 2006)

  • Average territory size
    unknown cm^2

Home Range

There is little available information on home ranges for red-cheeked squirrels.

Communication and Perception

There is little available information on communication in red-cheeked squirrels. In general, squirrels have several kinds of vocalizations for various situations, such as when young call their mothers, when adult males attract females during the breeding season, and when individuals alarm each other of danger. Squirrels also communicate with each other using certain postures, movements, and pheromones. (Thorington and Ferrell, 2006)

Food Habits

Red-cheeked squirrels are both insectivorous and frugivorous, which is consistent with other tree squirrels. However, it is known that they avoid hard seeds and tough tree bark. This is different from Pallas's squirrels (Callosciurus erythraeus), which are one of the tree squirrels that eat insects and fruits, and have an overlapping range of red-cheeked squirrels. (Koyabu, et al., 2012)

  • Animal Foods
  • insects
  • Plant Foods
  • fruit

Predation

There is little available information about predation on red-cheeked squirrels. However, it is known that predators of squirrels include cats, canids, weasels and birds of prey, such as eagles, hawks, falcons, and owls. Common anti-predator adaptations of squirrels are camouflage and escape. The body color of many of squirrels matches the surrounding environment, which helps them hide from predators. The body color of red-cheeked squirrels is grey brown, which is thought to blend well into the forest background. Also, squirrels run away quickly when they detect predators. (Brown, et al., 2014; Gurnell, 1987; Thorington and Ferrell, 2006)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • unknown

Ecosystem Roles

There is little available information on ecosystem roles in red-cheeked squirrels. Squirrels in general have multiple ecosystem functions. First, they serve as important prey for various predators, including threatened or endangered species. Also, tree squirrels in particular help disperse seeds through their caching activities. At the same time, tree squirrels are major predators of seeds. They often consume seeds in trees before seeds are fully mature, which can have a negative influence on trees via bark stripping and twig clipping. However, these features may not apply to red-cheeked squirrels, since it is reported that they avoid hard seeds and tough tree bark. In addition, squirrels are host to various parasites, including mites and ticks. (Gurnell, 1987; Lambert, et al., 2004; Thorington and Ferrell, 2006)

Species Used as Host
  • None
Mutualist Species
  • unknown
Commensal/Parasitic Species
  • unknown

Economic Importance for Humans: Positive

Red-cheeked squirrels are harvested for food. Particularly, this species is heavily hunted in Lao PDR and in some neighboring countries. (Duckworth, 2017; Timmins and Duckworth, 2008)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse effects of red-cheeked squirrels on humans.

Conservation Status

The population of red-cheeked squirrels is currently stable and this species is listed as Least Concern on the IUCN Red List. No major threats are detected in this species in Southeast Asia. However, this species is data deficient regarding population sizes and densities, so their conservation status might not be accurate enough. Given that this species is hunted for food, more rigorous monitoring of populations is important. (Duckworth, 2017; Koyabu, et al., 2012; Timmins and Duckworth, 2008)

Other Comments

There are six species under the genus Dremomys (plain long-nosed squirrels). (Hawkins, et al., 2016)

Contributors

Yuka Sugiura (author), University of Washington, Laura Prugh (editor), University of Washington, Galen Burrell (editor), Special Projects.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Brown, E., A. Peri, N. Santarosa. 2014. "Sciuridae" (On-line). Animal Diversity Web. Accessed May 10, 2019 at https://animaldiversity.org/accounts/Sciuridae/.

Can, D., H. Endo, N. Son, T. Oshida, L. Cahn, D. Phuong, D. Lunde, S. Kawada, A. Hayashida, M. Sasaki. 2008. Checklist of Wild Mammal Species of Vietnam. Kyoto: Shoukadoh.

Corbet, G., J. Hill. 1992. The Mammals of the Indo-Malayan Region: A Systematic Review. Oxford: Oxford University Press.

Davies, N., J. Krebs, S. West. 2012. An Introduction to Behavioural Ecology. New Jersey: Wiley-Blackwell.

Duckworth, J. 2017. "Dremomys rufigenis" (On-line). The IUCN Red List of Threatened Species 2017. Accessed May 10, 2019 at https://www.iucnredlist.org/species/6824/22256057#taxonomy.

Duckworth, J., R. Salter, K. Khounboline. 1999. "Wildlife in Lao PDR: 1999 Status Report" (On-line). Accessed May 10, 2019 at https://www.iucn.org/content/wildlife-lao-pdr-1999-status-report.

Endo, H., J. Kimura, T. Oshida, B. Stafford, W. Rerkamnuaychoke, T. Nishida, M. Sasaki, A. Hayashida, Y. Hayashi. 2003. Geographical variation of skull morphology and its functional significances in the red-cheeked squirrel. The Journal of Veterinary Medical Science, 65(11): 1179-1183.

Francis, C. 2008. A Guide to the Mammals of Southeast Asia. Princeton: Princeton University Press.

Gurnell, J. 1987. The Natural History of Squirrels. New York: Facts on File.

Hawkins, M., K. Helgen, J. Maldonado, L. Rockwood, M. Tsuchiya, J. Leonard. 2016. Phylogeny, biogeography and systematic revision of plain long-nosed squirrels (genus Dremomys, Nannosciurinae). Molecular Phylogenetics And Evolution, 94: 752-764.

Hayssen, V. 2008b. Patterns of Body and Tail Length and Body Mass in Sciuridae. Journal Of Mammalogy, 89(4): 852-873.

Hayssen, V. 2008a. Reproductive effort in squirrels: ecological, phylogenetic, allometric, and latitudinal patterns. Journal Of Mammalogy, 89(3): 582-606.

Koyabu, D., T. Oshida, N. Dang, D. Can, J. Kimura, M. Sasaki, M. Motokawa, N. Son, A. Hayashida, Y. Shintaku, H. Endo. 2009. Craniodental mechanics and the feeding ecology of two sympatric callosciurine squirrels in Vietnam. Journal of Zoology, 279(4): 372-380.

Koyabu, D., T. Oshida, S. Nguyen, C. Dang, N. Nguyen, M. Motokawa, J. Kimura, M. Sasaki, H. Endo, D. Nguyen. 2012. Comparison of Jaw Muscle Morphology in Two Sympatic Callosciurine Squirrels (Callosciurus Erythraeus and Dremomys Rufigenis) in Vietnam. Mammal Study, 37(3): 237-242.

Lambert, J., P. Hulme, S. Vander Wall. 2004. Seed Fate: Predation, Dispersal, and Seedling Establishment. Oxfordshire: CABI.

Nowak, R. 1999. Walker’s Mammals of the World. Vol. 1. Baltimore: The Johns Hopkins University Press.

Smith, A., Y. Xie. 2008. A Guide to the Mammals of China. Princeton: Princeton University Press.

Thorington, R., K. Ferrell. 2006. Squirrels - The Animal Answer Guide. Baltimore: The Johns Hopkins University Press.

Timmins, R., j. Duckworth. 2008. Diurnal squirrels (Mammalia: Rodentia: Sciuridae) in Lao PDR: distribution, status and conservation. Tropical Zoology, 21(1): 11-56.

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