Ratufa bicolorblack giant squirrel

Geographic Range

Black giant squirrels are found across much of the Oriental region. Their native range spans from northern Nepal and southern China through Vietnam. They are also numerous across the Malaysian Peninsula (Endo et al., 2004). For this reason they are also referred to as Malayan giant squirrels. (Endo, et al., 2004)

Habitat

Black giant squirrels are only found in heavily forested areas. Their range spans from sea level to as high as 2000 m. Since they are highly susceptible to deforestation, they are rarely found in degraded areas ("Wildlife in Lao PDR: 1999 Status Report", 1999). These squirrels are commonly seen between elevations of 1900 m and 2000 m, most frequently in areas rich in Vietnamese white pine, Pinus dalatensis (Abramov, Rozhnov and Morozov, 2006). Often, they are found nesting in the canopy of tall trees (Harrison and Traub, 1950). (Abramov, et al., 2006; Harrison and Traub, 1950)

  • Range elevation
    0 to 2000 m
    0.00 to 6561.68 ft

Physical Description

Black giant squirrels are characterized by their distinct size and pelage. With masses of 1546 g and lengths of 798 mm (head to tail), black giant squirrels are one of the largest members of the squirrel family (Thorington and Heaney, 1981). They are identifiable by their black fur, tan chest patch and occasionally tan tail tip. As is the case with most tree squirrels they do not exhibit sexually dimorphic. Unlike many squirrels, black giant squirrels do not have a tail that curls over its back. Instead, their tail lays limp behind them (Dobroruka, 1975). (Dobroruka, 1975; Thorington and Heaney, 1981)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    1546 g
    54.48 oz
  • Average length
    798 mm
    31.42 in

Reproduction

Mating behavior of black giant squirrels have only been studied with a few select captive pairs. However, several commonalities have been witnessed. Courtship behaviors include scent marking, chasing, nest building and grooming. Scent marking involves both male and females pressing their anogenital region against an object or the ground and urinating while moving slowly forward (Paulraj, 1988). Chasing involves males pursuing the female while she runs and hides. Often, this gives less dominant males a chance to find her before they can be chased off by older males (Thorington and Ferrell, 2006). (Paulraj, 1988; Thorington and Ferrell, 2006)

The mating systems for black giant squirrels in the wild have not been well studied. However, like many other solitary tree squirrels it is known to be polygynandrous (Dobroruka, 1975). Similar Malaysian tree squirrels are also polygynandrous. Their mating systems are assumed to reflect those of close relatives, Indian giant squirrels. For other close relatives, plantain and gray-bellied squirrels, when a female comes into estrous, six to eight males will come to the area early in the morning. During a several hour mating bout, five to seven males will copulate with the female. Males frequently attempt to chase off other males when in close proximity to the female (Tamura, 1993). Since several males will copulate with the female, it is not uncommon for siblings of the same litter to have different paternity (Thorington and Heaney, 1981). Squirrels that inhabit similar ecological or energetic niches also have similar mating and reproductive systems (Hayssen, 2008). (Dobroruka, 1975; Hayssen, 2008; Tamura, 1993; Thorington and Ferrell, 2006)

Black giant squirrels exhibit very similar reproductive behavior to most tree squirrel species. A female will give birth to one to two altricial young twice yearly. They have a gestation period that lasts an average of 31.5 days. After which, they will nurse their young for approximately five weeks. Like all members of the squirrel family, black giant squirrels reproduce sexually with the male impregnating the female during internal copulation. The reproductive efforts of all tree squirrel species take place in the canopy layer. This includes both nesting and mating efforts (Hayssen, 2008). Black giant squirrels give birth in two periods, from April to May and August to September (Hayssen, Tienhoven, and Tienhoven, 1993). (Hayssen, 2008; Hayssen, et al., 1993; Thorington and Ferrell, 2006)

  • Breeding interval
    Giant black squirrels breed twice yearly.
  • Breeding season
    Mating occurs from March to April or July to August.
  • Range number of offspring
    1 to 2
  • Average number of offspring
    1.44
  • Range gestation period
    28 to 35 days
  • Average weaning age
    5 weeks

Black giant squirrels give birth to altricial young that must be nursed; mothers provide this in the form of lactation. Males are only present for insemination and do not aid in parental care (Harrison and Traub, 1950). No evidence suggests that the young remain with the mother after they are weaned. (Harrison and Traub, 1950)

  • Parental Investment
  • altricial
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The average lifespan for black giant squirrels is 18 years in captivity. There are very few records detailing the lifespan of black giant squirrels all of which have been collected from captive, wild-born specimens. (Hayssen, et al., 1993; Pournelle, 1960)

  • Range lifespan
    Status: captivity
    19 (high) years
  • Average lifespan
    Status: captivity
    18 years

Behavior

Black giant squirrels are diurnal and known for their tendency to make its nests in the canopy of tall trees (Harrison and Traub, 1950). Like most tree squirrels they are a solitary animals, although they occasionally are seen in groups or pairs during the breeding season. Black giant squirrels do not form hierarchical groups (Dobroruka, 1975). Unlike ground squirrels, tree-living species do not hibernate. All tree species of squirrels (including black giant squirrels) are active during all parts of the year (Thorington and Ferrell, 2006). (Datta and Goyal, 2008; Dobroruka, 1975; Harrison and Traub, 1950; Thorington and Ferrell, 2006; Timmins and Duckworth, 2008)

Home Range

Black giant squirrels will forage on the ground for fruit and nuts extending their range below their normal habitat in the canopy (Meijaard and Sheil, 2008). However, the size of their home range is not known. (Meijaard and Sheil, 2008)

Communication and Perception

The specific communication systems of black giant squirrels have not been studied thoroughly. However, they likely communicate in much the same way as other members of the squirrel family. This means that they communicate through a series of vocal chirps and barks. In other Malaysian squirrel species, communication plays a large role in mating systems. Males locate and attract females using ultrasonic sounds. They will also bark post copulation for several minutes (Tamura, 1993). When courting, both genders will scent mark using urination to attract members of the opposite sex and show availability (Paulraj, 1988). As with many squirrels, they use alarm calls when they see a predator (Thorington and Ferrell, 2006). (Paulraj, 1988; Tamura, 1993; Thorington and Ferrell, 2006)

Food Habits

Like most squirrels, black giant squirrels eat fruits and nuts. Little is known about their foraging activity and the amount of food they consumes (Meijaard and Sheil, 2006). Locals within its range insist that they frequent their orchards (Harrison and Traub, 1950). (Harrison and Traub, 1950; Meijaard and Sheil, 2008)

  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

Black giant squirrels are preyed upon by several species. They live in the upper canopy, which allows them to avoid many ground predators (Harrison and Traub, 1950). However, this puts them at risk of predation from birds of prey such as Wallace's hawk eagle, which preys on arboreal mammals in Southeast Asia (Haring et al., 2007). Black giant squirrels are also at risk of predation by snakes when in the canopy. In order to collect food on the forest floor, they will occasionally move down from the canopy (Meijaard and Sheil, 2008); during which they are at risk of predation from terrestrial carnivores. However, the specific species that eat black giant squirrels have not been thoroughly studied. (Haring, et al., 2007; Meijaard and Sheil, 2008; Tamura, 1993; Thorington and Ferrell, 2006)

Black giant squirrels have several means of predator avoidance. As mentioned before, the location that they live in is out of reach of many terrestrial predators (Harrison and Traub, 1950). Also, as with many squirrels, they will use alarm calls when they see a predator. Their fur also provides camouflage, similar to many other squirrels. The ventral, or belly is a light color, while the dorsal, or back remains dark. This helps them blend in with the changing light patterns of the forest layers and avoid being seen from both terrestrial and aerial predators (Thorington and Ferrell, 2006). (Harrison and Traub, 1950; Thorington and Ferrell, 2006)

  • Known Predators
    • snakes (Serpentes)
    • Wallace's hawk eagle (Nanus wallace)
    • birds of prey (Falconiformes)

Ecosystem Roles

Because of their affinity for fruit and nuts black giant squirrels disperse seeds of large-seeded tree species. More specifically, these squirrels are known to disperse Burseraceae seeds (Canarium euphyllum; Kitamura et al., 2006). (Kitamura, et al., 2006)

  • Ecosystem Impact
  • disperses seeds
Mutualist Species
  • Burseraceae trees (Canarium euphyllum)

Economic Importance for Humans: Positive

Black giant squirrels were, until recently sold in large quantities at fresh food markets in Vientiane, Loas. At the time, they were one of the most commonly found specimens in several markets. In recent years, they are not as abundant in these markets due to declining wild populations ("Wildlife in Lao PDR: 1999 Status Report", 1999). ("Wildlife in Lao PDR: 1999 Status Report", 1999)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Black giant squirrels have been known to steal fruit from local orchards. (Harrison and Traub, 1950) (Harrison and Traub, 1950)

  • Negative Impacts
  • crop pest

Conservation Status

Black giant squirrels are susceptible to hunting and deforestation. they are in decline mainly due to over-hunting and secondarily due to habitat loss (Timmins and Duckworth, 2008). Historically, they have been sold in fresh food markets in Loas ("Wildlife in Lao PDR: 1999 Status Report", 1999). Black giant squirrels are significantly less abundant or not present in logged forests and plantation areas. This reduction in number is strongly correlated to the reduction in canopy cover and tree density (Datta and Goyal, 2008), because black giant squirrels nest in the high canopy layer of tall trees (Harrison and Traub, 1950). (Datta and Goyal, 2008; Harrison and Traub, 1950; "Wildlife in Lao PDR: 1999 Status Report", 1999; Timmins and Duckworth, 2008)

Contributors

Michelle Sutton (author), University of Alaska Fairbanks, Laura Prugh (editor), University of Alaska Fairbanks, Laura Podzikowski (editor), Special Projects.

Glossary

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.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

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.

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

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

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

oriental

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

World Map

polygynandrous

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

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

sexual

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

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

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

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

ICUN. 1999. "Wildlife in Lao PDR: 1999 Status Report" (On-line pdf). Accessed January 27, 2013 at http://data.iucn.org/dbtw-wpd/edocs/2000-050.pdf.

Abramov, A., V. Rozhnov, P. Morozov. 2006. Notes on Mammals of the Ngoc Linh Nature Reserve (Vietnam, Kon Tum Province). Russian Journal of Theriology, 5/2: 85-92.

Datta, A., S. Goyal. 2008. Responses of Diurnal Tree Squirrels to Selective Logging in Western Arunachal Pradesh. Current Science, 95/7: 895-902.

Dobroruka, L. 1975. Notes on the behaviour of the Malayan giant squirrel. International Zoo Yearbook, 15/1: 207-212.

Endo, H., J. Kimura, T. Oshida, B. Stafford, W. Rerkamnuaychoke, T. Nishida, M. Sasaki, A. Hayashida, Y. Hayashi. 2004. Geographical Variation of Skull Size and Shape in Various Populations in the Black Giant Squirrel. Journal of Veterinary Medical Science, 66/1: 213-218.

Haring, E., K. Kvaløy, J. Gjershaug, N. Røv, A. Gamauf. 2007. Convergent evolution and paraphyly of the hawk-eagles of the genus Spizaetus (Aves, Accipitridae) – phylogenetic analyses based on mitochondrial markers. Journal of Zoological Systematics and Evolutionary Research, 45/4: 353–365.

Harrison, J., R. Traub. 1950. Rodents and Insectivores from Selangor, Malaya. Journal of Mammalogy, 31/3: 337-346.

Hayssen, V. 2008. Reproductive effort in squirrels: ecological, phylogenetic, allometric, and latitudinal patterns.. Journal of Mammalogy, 89/3: 582–606.

Hayssen, V., A. Tienhoven, A. Tienhoven. 1993. Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-specific Data. Ithaca, NY: Cornell University Press.

Kitamura, S., S. Suzuki, T. Yumoto, P. Poonswad, P. Chuailua, K. Plongmai, T. Maruhashi, N. Noma, C. Suckasam. 2006.

Dispersal of Canarium euphyllum (Burseraceae), a large-seeded tree species, in a moist evergreen forest in Thailand
. Journal of Tropical Ecology, 22/2: 137-146.

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 Research, 23/1: 21-34.

Paulraj, S. 1988. Breeding behaviour of the Malay giant squirrel Ratufa bicolor at Arignar Anna Zoological Park. International Zoo Yearbook, 27/1: 279–282.

Pournelle, G. 1960. Some longevity records of captive mammals. Journal of Mammalogy, 41/1: 114.

Tamura, N. 1993. Role of Sound Communication in Mating of Malaysian Callosciurus (Sciuridae). Journal of Mammalogy, 74/2: 468-476.

Thorington, R., K. Ferrell. 2006. Squirrels : the animal answer guide. Baltimore, Maryland: The Johns Hopkins University Press.

Thorington, R., L. Heaney. 1981. Body Proportions and Gliding Adaptations of Flying Squirrels (Petauristinae). Journal of Mammalogy, 62/1: 101-114.

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