Gambian sun squirrels, Heliosciurus gambianus, are found only in the tropical regions of Africa. The range of this species range stretches from Nigeria and Senegal on the west coast, across to the eastern coasts of Sudan, Uganda, Kenya, and Ethiopia. A few populations have been found in Angola, the Congo, and Zambia. (Kingdon, 1974; Rosevear, 1969)
Gambian sun squirrels prefer to live in tall, dense woodland savanna. They are arboreal, and are slowly expanding into the rainforests. Although they prefer staying in the upper branches of trees, they will also feed on lower branches and even on the ground. In addition to the savannas and rainforests, they are found in woody water courses and thickets. (Happold, 1987; Kingdon, 1974; Rosevear, 1969)
Long and slender, H. gambianus has a small head coming to a bluntly pointed muzzle. The ears are round, and the eyes are large and bright. These animals weigh between 250 and 340 g, and measure in at 153 to 210 mm. The sexes are reported to be the same size, and to possess the same pelage.
There are at least seven different sub-species of Gambian sun squirrels, and all are distinguished almost solely by differences in color. Because of this variety, it is difficult to describe the appearance of these animals except in broad terms and in comparison to other species of sun squirrel.
In general, H. gambianus is duller than other squirrels found in western Africa. Its dorsal pelage and flanks are grey, grey-brown or honey-colored and can have black speckling. There is a distinct black line that travels from the head to the tail, flanked on either side by a wide honey colored band. The tail has a black tip and the throat, chest, and ventral pelage are white. The tail is ringed with alternating black and tan rings.
Punctate sun squirrels, H. gambianus punctatus, live in moister forest climates and have darker pelage, with some intermingled honey-colored hairs. The ventral pelage is more grey than white, and is a little longer and softer than the typical H. gambianus.
Bongo sun squirrels, H. gambianus bongesis also live in moist forests and are colored similarly to punctate sun squirrels except that the crown, neck, and mid-dorsum are redder, and the tail bands are not as distinct. What sets this sub-species apart is the unusual red tinge on the insides of the thighs and the root of the tail.
Senegal sun squirrels, H. gambianus senescens, have very distinct rings on the tail, because the honey colored rings are a lighter, almost beige tone.
Schwarze's sun squirrels, H. gambianus imbatus, live mainly in forests on the banks of streams. The tail rings are faint and the flanks of this sub-species are lighter due to interspersed white hairs. There is some red in the dorsal pelage.
Montane sun squirrels, H. gambianus emissus, are a dark reddish sub-species. The tail is distinctive because of the greyish-black hair at the base of the back, leading into a long band of rusty-red thena long black ring, a short pale ring, and a short black tip.
Savanna sun squirrels, H. gambianus savannius, look like H. g. bongensis, except that they have no dorsal reddish hairs. This subspecies also has fainter rings on the tail and the tips of the tail hairs are very long and white.
Marra sun squirrels, H. gambianus canaster, differ from typical Gambian sun squirrels only because they are paler and there is a little bit of pink under the tail.
No information is currently available regarding the mating system of H. gambianus. However, another member of the genus, H. rufobrachium is often found in pairs. It is not known if these represent stable mating pairs, however, it raises the prospect that these squirrels could be monogamous. (Nowak, 1997)
Little is known about the reproductive habits of sun squirrels. However, the genus Heliosciurus is reported to have two breeding seasons in West Africa, July through September and November through January. The young of H. gambianus were collectd in February, and two pregnant females had one and five embryos. It has been noted that most squirrels in west Africa tend to have one to two young in each litter. It is not known how these data pertain to H. gambianus. (Nowak, 1997; Rosevear, 1969)
Parental investment is poorly documented and perhaps scarcely studied for H. gambianus. Like in all mammals, the pregnant female invests her energy in producing the young, and the litters are typically small. When just born, the neonates are basically helpless, and are completely dependent upon the parents. The mother will nurse them, but sun squirrels grow fast, and will reach adult age fairly quickly. As the young are growing, the mother offers food and protection, as well as teaches them what is good for consumption and what is better left alone. The role of males in parental care of this species has not been documented. (Rosevear, 1969)
Although populations can be quite dense, Gambian sun squirrels are for the most part solitary creatures. Occasionally a family group (the parents and one or two young) will be seen together. They are diurnal animals, and at night they sleep in holes lined with freshly gathered leaves. For the most part they are arboreal, preferring the higher strata of the trees to the lower strata or the ground.
Like most squirrels, Gambian sun squirrels are confident climbers and leap with agility between trees. On the ground, their gait is a series of small leaps, the two hindfeet and two forefeet alternating as pairs.
Most observations of H. gambianus have been in captivity, and their behavior is interestingly divergent from their behavior in the wild. For example, in captivity they are prone to sleeping with other animals, and other species if their own is not available. Also, they do not make nests in captivity. (Rosevear, 1969)
The home range size for these animals is not known.
Most observed communication has been recorded in captivity. Gambian sun squirrels emit a high-pitched squeak when they are eating and are afraid that they will be disturbed. The tail flicks when they sense danger, but this may simply be a reaction rather than a type of signal. They also squeak constantly when running around a room.
In the wild, these animals make other noises, such as a long note, "ker, ker," a short trill, and a chatter. The meanings of these calls are yet to be determined. It can be inferred that their hearing is quite good because of their medium sized external ear conch and sensitivity to dangerous sounding noises. (Rosevear, 1969)
In addition to vocal communications, it is likely that these animals use some visual and tactile communication, especially between mates, or between parents and offspring. Chemical communication has not been documented in this species.
Gambian sun squirrels have been seen eating everything from fruits, seeds, and the pods of Acacia species to insects, eggs, and young birds. They have even been recorded eating geckos, lizards, and nestlings. Rosevear infers that if the opportunity should arise, small mammals would also be killed and eaten. H. gambianus especially likes oil palm nuts, and prefers the husk to the kernal. The foraging behavior of these animals helps to wear down their ever-growing incisors. Gnawing through tree bark and the tough husks of some fruits apparently helps their teeth. (Delany, 1975; Kingdon, 1974; Rosevear, 1969)
Genets and palm civets are noted as an adults squirrel's most likely predator. The young are likely to fall prey to rats, snakes, and driver ants. Parents are known to cover the entrance to their nest with loose twigs and leaves, but this is easily bypassed. The parents may sometimes save the young from ants by carrying them in their mouth to a safer place. (Rosevear, 1969)
The most significant impact that this species has on its ecosystem is most likely the result of its eating habits. Its daily diet of nuts and fruits plays a role in the destruction and dispersal of seeds. They are small mammals, and therefore probably have voracious appetites. Even though their diet is, for the most part, varied, their presence is surely felt by the insects and birds they prey on. (Rosevear, 1969)
This squirrel has little impact on its human neighbors. At times their skins were made into small bags, but it is now rarely done. They were also once considered a food source, but that was only for a brief period. Perhaps their greatest contribution to humans is by becoming pets. Squirrels make good pets, as long as they are taken before they are weaned. (Rosevear, 1969)
There are no known significant adverse affects of H. gambianus on humans. Predators abound in the tropics, so they have little chance of becoming pests. They eat palm oil nuts, and sometimes cocoa pods, but not in enough numbers to be a nuisance. (Rosevear, 1969)
H. gambianus is known to coexist quite peacefully with humans as well as other species of squirrels, and as a result is quite common in the tropics of Africa. Gambian sun squirrels are currently not listed as threatened or endangered.
Nancy Shefferly (editor), Animal Diversity Web.
Alice Park (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
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.
Referring to an animal that lives in trees; tree-climbing.
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.
uses smells or other chemicals to communicate
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.
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
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).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
the business of buying and selling animals for people to keep in their homes as pets.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
Delany, M. 1975. The Rodents of Uganda. Kettering Northamptonshire: British Museum (Natural History).
Happold, D. 1987. The Mammals of Nigeria. Oxford: Clarendon Press.
Kingdon, J. 1974. East African Mammals. Chicago: The University of Chicago Press.
Nowak, R. 1997. "Sun Squirrels" (On-line). Walker's Mammals of the World. Accessed February 12, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/rodentia/rodentia.sciuridae.heliosciurus.html.
Rosevear, D. 1969. The Rodents of West Africa. London: Trustees of the British Museum (Natural History).