Ratufa affinis

Geographic Range

Cream-coloured giant squirrels ( Ratufa affinis ) are present throughout Southeast Asia, specifically peninsular Malaysia, Indonesia and Thailand, as well as the islands of Borneo, Singapore and Sumatra. However, there is growing evidence that their range is shrinking due to logging and habitat destruction, especially in Borneo. Forest acreage is decreasing at a substantial rate, even in areas that are considered protected. Populations are also decreasing in density.

• Biogeographic Regions
• oriental oriental
  • native native

Habitat

Cream-coloured giant squirrels are arboreal. They spend their lives in the treetops of tropical forests and only go to ground level to reach trees that are not accessible from the canopy, or to escape predators. These animals are often observed residing within the middle of the tree canopy in lowland and hill forests with tall trees, they are not often found in agricultural areas. Southeast Asia, the habitat region of cream-coloured giant squirrels, is covered in tropical rainforests with a variety of plant life including shrubs, flowering plants, a wide variety of dipterocarps and other fruiting plants, like strangler figs. These regions have typical wet and dry seasons.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

Physical Description

The world’s largest tree squirrels are included in genus Ratufa . Cream-coloured giant squirrels share a similar appearance and shape to other squirrel species, but differ in their size and coloration. Their weight ranges from 929 to 1,575 g and their head and body length is 322 to 350 mm, not including their tail. Their tails, which hang vertically when they are seated and extends horizontally while they are running, are longer than their bodies, ranging from 373 to 438 mm, giving them an overall length of more than 610 mm. Their coloration varies by location. Historically, 37 subspecies of cream-coloured giant squirrels have been described; however, 9 geographically and physically distinct subspecies are currently recognized. In general, these animals have orange to brown dorsal pelage and buffy to white ventral pelage, with a black tail, white cheeks and a thin black moustache. However, in Borneo and northern regions, these animals tend to be darker as compared to their paler counterparts found in the southern portions of their range.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

Reproduction

At present, very little is known about the mating systems of cream-coloured giant squirrels. The only studies presently available are in reference to captive individuals from closely related black giant squirrels ( Ratufa bicolor ). Newly introduced captive mates often begin building twig nests shortly after being housed together. Wild born captive pairs displayed distinct mating behaviors such as scent marking, chasing and grooming. Males inspect the female’s genitals before engaging in pre-copulatory chases after which, the males attempt to mount, if permitted, mating lasts about 1 to 3 seconds. The specific mating systems of this species are not known, however, most squirrel species engage in a polygynous mating system, although some species engage in a polygynandrous system as well.

The gestation length of cream-coloured giant squirrels has not been reported, however, there appears to be a large variation in the gestation period of genus Ratufa . Grizzled giant squirrels ( Ratufa macroura ) have a reported 28-day gestation period, Black giant squirrels ( Ratufa bicolor ) have a 32-day gestation period and Indian giant squirrels ( Ratufa indica ) have a staggering 84-day gestation period. The lactation period for black giant squirrels has been reported at 35 days versus the 63-day period reported for grizzled giant squirrels. Cream-coloured giant squirrels have been noted to have litters that include 3 offspring. Captive black giant squirrels weigh between 75 and 77 grams at birth and first emerge from their nest 33 days after birth. In general, this genus has short gestation and lactation rates, relative to their size. Members of this genus typically only produce 2 litters per year, although they may be reproductively active throughout the year.

• Key Reproductive Features
• semelparous semelparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

At this time, little information is known regarding the parental investment of cream-coloured giant squirrels. Both sexes participate in the construction of a large, round twig nest in the canopy, where young are born and raised. These nests are very large, similar in size to eagle aeries. In captivity, female black giant squirrels ( Ratufa bicolor ) wash, defend, move their young and repair and improve their nest. Due to their short gestation and lactation lengths, as well as their potentially year-round breeding, these animals have been described as using minimal but constant effort for breeding.

• Parental Investment
• female parental care female parental care

Lifespan/Longevity

At this time, there is no data regarding the lifespan of cream-coloured giant squirrels. However, the maximum captive lifespan has been estimated for other members of their genus. Indian giant squirrels ( Ratufa indica ) may live up to 20 years in captivity and black giant squirrels ( Ratufa bicolor ) may live up to 19 years.

Behavior

Cream-coloured giant squirrels are solitary. Social interaction usually only occurs during mating season, during which time, they are seen only in pairs. They are arboreal and spend the vast majority of their time in the forest canopy, using the dense foliage as protection from predators. When threatened they bristle their fur and make loud calls. These animals are diurnal; they are active after dawn and return to their nests before dusk. Their nests usually have a globular shape and are found in the crown of tall trees.

• Key Behaviors
• arboreal arboreal
• diurnal diurnal
• motile motile
• solitary solitary

Home Range

The home range size of cream-coloured giant squirrels has not been reported, however, there are typically 11 individuals found per km2.

Communication and Perception

In general, squirrels mark their territory by scratching and removing bark from tree branches and marking these areas with urine. Both male and female cream-coloured giant squirrels have been noted scent marking by dragging their anogenital region across territory areas. During territorial scent marking, the animals release a very small amount of urine, as opposed to the scent marking performed by females in estrus, which involves a larger release of urine. Cream-coloured giant squirrels produce a variety of vocalizations including a staccato mating call, harsh chatter, which can be heard for several meters and is likely used territorially and a much softer “hgip…hgip” call, whose function is unknown.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Cream-coloured giant squirrels find the majority of their food in tree tops, where they spend most of their time. These animals primarily consume plant parts such as leaves, fruit, bark and seeds; however, they also consume insects. Dipterocarp seeds play a larger role in their diet during periods of mast fruiting, when large amounts of seeds are produced and deposited. While eating, cream-coloured giant squirrels allow their tail to hang down, using it as a counterbalance, this leaves their hands free for manipulating food.

• Primary Diet
• omnivore omnivore

• Animal Foods
• eggs
• insects

• Plant Foods
• leaves
• wood, bark, or stems
• seeds, grains, and nuts
• fruit

Predation

Cream-coloured giant squirrels face predation from a variety of predators including cats, snakes, raptors and humans. Because they are arboreal, their main threats are birds, such as crested serpent eagles ( Spilornis cheela ). Their defense behaviors include bristling their fur and darting for cover, while calling loudly. Indigenous people often use the squirrel as a food source, hunting with shotguns and blowpipes.

Ecosystem Roles

Cream-coloured giant squirrels are a food source for larger predators, such as birds of prey. Their role in the seed dispersal of mast-fruiting trees like dipterocarps has been studied, however, fruit is not their preferred food source and is only consumed when other food is lacking.

Economic Importance for Humans: Positive

Although human use of this species appears to be limited, cream-colored giant squirrels are hunted and eaten by native people.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known negative impacts of this species on human populations.

Conservation Status

Currently, cream-coloured giant squirrels are classified as ‘near threatened’ by the IUCN, with a decreasing trend in the global population. The largest factor behind these population declines appears to be loss of habitat throughout their range due to human related activities. Studies of protected forest sites in Borneo show that areas under protection show a higher rate of forest loss than those outside of the boundary. Removal of large trees is especially detrimental, as they are used by this species for nesting and feeding.

Additional Links

Encyclopedia of Life

Contributors

Jessica Branson (author), Northern Michigan University, Leila Siciliano Martina (author), Texas State University, John Bruggink (editor), Northern Michigan University.

References

Aparajita, D., S. Goyal. 1996. Comparison of Forest Structure and Use by the Indian Giant Squirrel (Ratufa indica) in Two Riverine Forests of Central India. Biotropica , 28: 394-399.

Becker, P., M. Leighton, J. Payne. 1985. Why Tropical Squirrels Carry Seeds Out of Source Crowns. Journal of Tropical Ecology , 1: 183-186.

Curran, L., M. Leighton. 2000. Vertebrate Responses to Spatiotemporal Variation in Seed Production of Mast-Fruiting Dipterocarpaceae. Ecological Society of America , 70: 101-128.

Duckworth, J., E. Meijaard, B. Giman, K. Han. 2008. "Ratufa affinis" (On-line). IUCN Red List of Threatened Species. Accessed April 01, 2013 at http://www.iucnredlist.org/details/19376/0 .

Francis, C. 2008. A Field Guide to the Mammals of South-East Asia . London: New Holland Publishers.

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

Hayssen, V. 2008. Reproductive effort in squirrels: Ecological, phylogenetic, allometric, and latitudinal patterns. Journal of Mammology , 89:3: 582-606.

MacKinnon, K. 1996. The Ecology of Kalimantan: Indonesian Borneo . United Kingdom: Oxford University Press.

McConkey, K., D. Chivers. 2004. Low mammal and hornbill abundance in the forests of Barito Ulu, Central Kalimantan, Indonesia. Oryx , 38: 439-447.

Meijaard, E., D. Sheil. 2008. The persistence and conservation of Borneo's mammals in lowland rain forests managed for timber: observations, overviews and opportunities. Ecological Restoration , 23: 21-34.

Nakagawa, M., Y. Takeuchi, T. Kenta, T. Nakashizuka. 2005. Predispersal Seed Predation by Insects vs. Vertebrates In Six Dipterocarp Species in Sarawak, Malaysia. Biotropica , 37: 389-396.

Ng, P., R. Corlett, H. Tan. 2011. Singapore Biodiversity: An Encyclopedia of the Natural Environment and Sustainable Development . Singapore: Editions Didier Millet.

Paulraj, S. 1988. Breeding behaviour of the Malay giant squirrel Ratufa bicolor at Arignar Anna Zoological Park. International Zoo Yearbook , 27: 279-282.

Saiful, A., M. Nordin. 2004. Diversity and Density of Diurnal Squirrels in a Primary Hill Dipterocarp Forest, Malaysia. Journal of Tropical Ecology , 20: 45-49.

Sherman, P., L. Wauters. 2001. Squirrels. Pp. 598-608 in The Encyclopedia of Mammals , Vol. 1. London: The Brown Reference Group.

Tacutu, R., T. Craig, A. Budovsky, D. Wuttke, G. Lehmann, D. Taranukha, J. Costa, V. Fraifeld, J. de Magalhaes. 2013. "An Age: The Animal Aging and Longevity Database" (On-line). Human Aging Genomics Resources: Integrated databases and Tools for the Biology and Genetics of Aging. Accessed September 22, 2013 at http://genomics.senescence.info/species/ .

Willis, R. 1980. Breeding the Malayan giant squirrel Ratufa bicolor at London Zoo. International Zoo Yearbook , 20:1: 218-220.

Royal Society SEARRP. 2013. "Giant Squirrel (Ratufa Affinis)" (On-line). Stability of Altered Forest Ecosystems. Accessed February 18, 2013 at http://www.safeproject.net/animal-sightings/giant-squirrel-ratufa-affinis/ .