Red-bellied squirrels naturally inhabit southern China, Malaya, and the lowlands and mountains of Taiwan. In 1935, 40 individuals were removed from Taiwan and introduced on the island of Izuoshima, about 100 km south of Tokyo, Japan. Later, 100 squirrels were taken from the Izuoshima population and moved 400 km west to Tomogashima Island. (Setoguchi 1990)
Biogeographic Regions: oriental (Introduced , Native )
Callosciurus erythraeus are medium in size with adults reaching a total head and body length of up to 200 mm. They have strong claws on their fingers and toes, excellent for digging holes to cache a supply of nuts. The ankles have extreme rotational capability and the claws, which they sink into the bark of a tree branch or trunk as they run, ensure them a firm grip as they chase nimbly through the trees. With large, protruding eyes, red-bellied squirrels have sharp vision and can distinguish vertical objects particularly well -- a useful ability for an animal that spends much of its time in trees leaping from branch to branch. Because of eye location, they are able to see behind, overhead and underneath without turning their heads, giving them the ability to survey the area for any signs of danger. The eyes also contain cones within the retina, allowing Callosciurus erythraeus to see the bright colors of its surroundings. (NatZoo 1992)
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Average mass: 272 g.
Habitat and Ecology
The habitat has a mean temperature of 15.8 degrees Celsius and mean rainfall of 1,455 mm. Vegetation consists of warm-temperate evergreen trees and woody plants with a high occurrence of fruiting vegetation such as the camellia and bayberry.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest ; rainforest
Similar to all tree squirrels, red-bellied squirrels rely heavily on a diet consisting of leaves, fruit, seeds, insects, nuts, acorns, and cones. These squirrels feed mainly in the trees, but do spend some time feeding on the surface. Clearly they rely most heavily on arboreal foods and procure most foodstuffs while keeping their place among the branches. Red-bellied squirrels are well adapted in that they rotate their dietary consumption based on the seasonal availability of the item. In winter, they consume primarily Camellia tree flowers, which bloom from October to June. Later the diet switches toward the greatest period of leaf consumption from April to May. In June their palate is suffused with the luscious fruits that are now abundant. And as fall comes around, red-bellied squirrels busy their jaws with the nutritiously profitable food source of ants that are still active above ground as opposed to the usual hoarding behavior. (Setoguchi 1990)
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts; fruit
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Frugivore , Granivore )
Red-bellied squirrels are important as seed dispersers of tree species.
Ecosystem Impact: disperses seeds
Known prey organisms
This list may not be complete but is based on published studies.
Life History and Behavior
Status: captivity: 16.1 years.
Lifespan, longevity, and ageing
Red-bellied squirrels are sexually promiscuous. On the female's day of estrus, several males gather around her and begin vocalizing. These vocalizations are the beginning of mating bouts in which the males spar with one another to win the right to mate. The winner of the bout will often guard his mate for a short period of time, trying to ensure that he is the true fertilizer of the female's eggs. But if the number of challenging males gets to be too much, the "guard" usually leaves and she may mate (and usually does) with another individual.
Mating System: polygynandrous (promiscuous)
The female first scouts and then builds a nest in a suitable and relatively protected site. This behavior peaks in spring and autumn in accordance with the breeding seasons. In that nest, the female gives birth usually to several young.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); oviparous
Young are cared for and nursed by females in the nest until they reach independence.
Parental Investment: altricial ; female parental care
Molecular Biology and Genetics
Barcode data: Callosciurus erythraeus
No available public DNA sequences.
Download FASTA File
Statistics of barcoding coverage: Callosciurus erythraeus
Public Records: 4
Specimens with Barcodes: 5
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
There is no threat to this species as they have been widely introduced from their ancestral home ranges to new localities such as Tomogashima Island. Numbers there have increased profoundly and these squirrels had colonized the whole island by 1959, only 5 years after being first introduced.
IUCN Red List of Threatened Species: least concern
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
The small negative effects of red-bellied squirrels lies primarily in their habit of gnawing on tree bark, sometimes killing the tree. Also their consumption of oil palm nuts has brought them into conflict with plantation owners who now hunt them as pests. (NatZoo 1992)
Negative Impacts: crop pest
Economic Importance for Humans: Positive
Red-bellied squirrels are valuable for their ecosystem roles, particularly as seed dispersers.
Pallas's squirrel is a medium-sized tree squirrel, with a head-body length of 16 to 28 cm (6.3 to 11.0 in), and a tail 11 to 26 cm (4.3 to 10.2 in) in length. Both sexes are of similar size and appearance, and weigh between 310 and 460 g (11 and 16 oz). The colour of the pelt varies considerably between the many different subspecies, but is generally brownish on the upper body with a more reddish tint on the belly, and often with some black on the tail. The precise pattern and shades of the fur are often used to distinguish subspecies from one another, but make it difficult to distinguish the species as a whole from other, similarly variable, tree squirrel species.
Over thirty subspecies have been identified, although not all are recognised by all authorities:
Distribution and habitat
Pallas's squirrel is found throughout much of southeastern Asia, including far eastern India, Bhutan, northern and eastern Myanmar, Vietnam, parts of Cambodia and Laos, much of Thailand, northern peninsular Malaysia, and southern and eastern China, including Taiwan. Within this region, they are found within a range of forest habitats below 3,000 m (9,800 ft) elevation, including tropical and subtropical evergreen, deciduous broadleaf, and subalpine conifer woodlands. There are also introduced populations in the Buenos Aires Province of Argentina, Belgium, Netherlands, France, and in Japan.
Like all tree squirrels, Pallas's squirrels are primarily herbivorous. They eat a wide range of different foods, and have differing diets in different parts of their broad range. However, primary foodstuffs include leaves, flowers, seeds, and fruit. They also eat small quantities of insects, as well as occasional bird eggs.
The squirrels breed throughout the year, and may mate again as soon as they have weaned a previous litter. Pregnancy lasts 47 to 49 days, and results in the birth of up to four young, with two being typical. The young leave the nest at 40 to 50 old, and are sexually mature at one year of age. They have lived for up to seventeen years in captivity.
Pallas's squirrels are diurnal, and inhabit much of the forest canopy, and construct both leaf nests 7 to 18 m (23 to 59 ft) above the ground, and, less commonly, underground burrows. Females occupy home ranges of just 0.5 to 0.8 hectares (1.2 to 2.0 acres), which usually do not overlap, while males occupy much larger ranges of 1.3 to 3.8 ha (3.2 to 9.4 acres), which overlap with those of both nearby males and females. Like many other squirrels, they have been observed to cache acorns in the autumn.
The squirrels make calls to warn neighbours of predators, and have been observed to mob tree-climbing snakes, with females protecting young being particularly likely to join in. Males also make loud calls prior to, and after, mating.
- Duckworth, J. W., Timmins, R. J. & Molur, S. (2008). Callosciurus erythraeus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 6 January 2009.
- Lurz, W.W., et al. (2013). "Callosciurus erythraeus (Rodentia: Sciuridae)". Mammalian Species 45 (902): 60–74. doi:10.1644/902.1.
- Xiao, Z., et al. (2009). "Behavioral adaptation of Pallas's squirrels to germination schedule and tannins in acorns". Behavioral Ecology 20 (5): 1050–1055. doi:10.1093/beheco/arp096.
- Koyabu, D.B., et al. (2009). "Craniodental mechanics and the feeding ecology of two sympatric callosciurine squirrels in Vietnam". Journal of Zoology 279 (4): 372–380. doi:10.1111/j.1469-7998.2009.00629.x.
- Setoguchi, M. (1991). "Nest-site selection and nest-building behavior of red-bellied tree squirrels on Tomogashima Island, Japan". Journal of Mammalogy 72 (1): 163–170.
- Tamura, N., et al. (1988). "Dominance hierarchy and mating behavior of the Formosan squirrel, Callosciurus erythraeus thaiwanensis". Journal of Mammalogy 69 (2): 320–331.
- Tamura, N. (1989). "Snake-directed mobbing by the Formosan squirrel Callosciurus erythraeus thaiwanensis". Behavioral Ecology and Sociobiology 24 (3): 175–180. doi:10.1007/BF00292100.
- Tamura, N. (1995). "Postcopulatory mate guarding by vocalization in the Formosan squirrel". Behavioral Ecology and Sociobiology 36 (6): 377–386. doi:10.1007/BF00177333.