As an inhabitant of a remote and poorly studied region of the world, very little is known about the ecology of the pygmy scaly-tailed flying squirrel, other than largely anecdotal accounts from chance encounters (3). It is certainly inactive during the day, passing the sunlit hours sheltering in hollow trunks and branches as much as 40 metres above the ground and in colonies of up to 100 individuals (3) (6). In contrast, during the night it is extremely energetic and may travel several kilometres to feed, climbing to the tops of trees, leaping off and gliding down to the trunk of another tree which in turn is ascended. With an impressively slow-rate of descent it is reportedly able to travel more than a 100 metres in a single glide (3) (5) (6) (7). Considered to be primarily herbivorous, the pulp of oil palm fruits is thought to be its main food source but it may also occasionally consume insects and possibly nectar (5) (6). Other than reports of female pygmy scaly-tailed flying squirrels leaving the colony to bear a single young, nothing is known about its reproductive biology (7). In other Anomalures, the female has two litters of one to three young per year, which at birth are active, have a full body of fur and open eyes (6) (7).

The pygmy scaly-tailed flying squirrel is the smallest of seven species of mainly gliding rodents belonging to the family Anomaluridae (4) (5). In common with all but one member of the family, the pygmy scaly-tailed flying squirrel has a membrane that extends along the sides of its body from limb to limb (3) (6) (7). Stretched out in flight, the membrane forms a square parachute, enabling these arboreal rodents to glide incredible distances from one tree to another (5) (7). This adaptation to life in the trees is akin to the flying membranes displayed by Australian flying possums and true flying squirrels but is actually the product of convergent evolution rather than close ancestry (3) (7). It has a fine silky coat, predominately tawny coloured but slightly paler along the neck and belly (3) (6). A small portion of the underside of its long, thin tail is covered with a roughened file-like surface that possibly aids in climbing the rough bark of trees (3) (6) (7). The upperpart of the tail is sparsely covered with long hairs (3) (6).

This Central African species has been reported from Cameroon and Equatorial Guinea (Rio Muni) in the west of its range, Ngotto forest on the border of the Central African Republic and Congo; and then in northeastern Democratic Republic of the Congo. It is possibly present in extreme western Uganda. The species possibly occurs more widely between the known populations. There is a population on Mount Cameroon (Cameroon), that is believed to be separate from the remainder of the range.

Idiurus zenkeri is found throughout Upper Cameroon to Rio Muni and Northwest Gabon. The range extends from the northeast and east portion of Zaire, east of the Lualaga to Lake Kivu, eastern Nigeria, the Gold Coast, Gabon, Liberia, and west Uganda.

Pygmy scaly-tailed flying squirrels are found in the following countries: Cameroon, Central African Republic, Congo, the Democratic Republic of the Equatorial Guinea, and Uganda.

Biogeographic Regions: ethiopian (Native )

The distribution of the pygmy scaly-tailed flying squirrel extends from southern Cameroon and Equatorial Guinea in the west, to the Democratic Republic of Congo and western Uganda in the east (3) (4) (8).

Pygmy scaly-tailed flying squirrels have a body length from 63 to 75 mm, tail length of 83 to 104 mm, hind foot length of 14 to 17 mm, ear length of 11 to 15 mm, and greatest length of skull of 22 mm. They are the smallest of the scaly-tailed squirrels. They have a feathery tail. Dorsal fur color is grey to brown and ventral fur color is whitish. A gliding membrane is located between the fore and hind limbs. Scaly-tailed squirrels have silky fur, long whiskers, and two rows of pine cone like scales on the underside of their tails. The top of the tail is covered with sparse, 2 cm long hairs. The tail has a row of short (2 to 3 mm), stiff hairs along both sides. The entire underside of the tail is hairless, with a 1.5 to 2.5 cm long rough, scaly patch that extends from the tail base. These scales typically act as anti-skid devices that also provide extra grip while climbing or support when resting. Sharp claws also provide extra grip.  The fur is fine, although less dense on the gliding membrane. The elbow has a cartilaginous extension that allows for greater freedom of movement in the upper limbs.

Average mass: 17.4 g.

Range length: 63 to 75 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Habitat and Ecology

Systems

• Terrestrial

Pygmy scaly-tailed flying squirrels are found in moist tropical and subtropical climates. They are arboreal, occurring mainly in forests composed of the following tree taxa: Klainedoxa species, Pseudoprosopis species, Paramacrolobium species, Gilbertiodendron species, and Pentaclethra species.

Range elevation: Primarily high forests (high) m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; rainforest

Dependant on mature trees for food and shelter, this rodent only occurs in dense tropical forests (3) (6).

Pygmy scaly-tailed flying squirrels are capable of traveling several kilometers in search of food. Foraging behaviors are probably similar to that of Idiurus macrotis. Pygmy scaly-tailed flying squirrels eat fruit, nuts, tree gums, and bark, including oil palm fruits. Anomalurids have relatively long digestive tracts, which allows for the maximum absorption of nutrients.

Plant Foods: wood, bark, or stems; seeds, grains, and nuts; fruit; sap or other plant fluids

Primary Diet: herbivore (Frugivore , Granivore )

Anomularids will chew off the tops of young, non-food tree species, resulting in a reduction of competition for their favored trees species and a change in the composition of forest trees. Pygmy scaly-tailed flying squirrels may also contribute to the dispersal of forest tree seeds when they eat fruit.

In 1968, four individuals of I. zenkeri were found nesting in a tree on Dipikar Island with two individuals of Anomalurus derbianus.

Mutualist Species:

• Lord Derby's scaly-tailed squirrels (Anomalurus derbianus)

There is little information on predators of pygmy scaly-tailed flying squirrels. Eagles have been known to prey on other scaly-tailed squirrel species and it is likely that birds of prey and arboreal snakes prey on scaly-tailed squirrels.

Known Predators:

• eagles and other birds of prey (Falconiformes)

Pygmy scaly-tailed flying squirrels emit a mouse-like squeak that is heard when individuals are disturbed. Communication by scent is important in anomularids. Large groin glands produce strong smelling secretions.

Pygmy scaly-tailed flying squirrels have large, forward facing eyes that provide excellent binocular vision and relatively large ears that support acute hearing that could include ultrasonic frequencies.

Communication Channels: acoustic ; chemical

Perception Channels: visual ; ultrasound

There is no information known about the longevity of I. zenkeri.

The mating system of Idiurus zenkeri is not reported.

There is little information on reproduction in Idiurus zenkeri. It is believed to be similar to Idiurus macrotis and other anomalurids. Young are precocial and born in litters of up to three young. Parents will finely chew food in their cheeks and then pass it on to their young during the weaning process. No pregnant females have been observed. It is thought that females may give birth to their young away from the colony.

Breeding interval: Breeding intervals are not known.

Breeding season: The breeding season of I. zenkeri is not reported.

Range number of offspring: 3 (high) .

Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Like all mammals, females I. zenkeri nurse and care for their young until they are weaned. Otherwise, little is known about the investment of male and female parents and length of dependence.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female)

In 1996, I. zenkeri was listed as lower risk/near threatened by the IUCN. This species is poorly known and has since been re-categorized as data deficient. Idiurus zenkeri populations are negatively impacted by timber harvesting and destruction of habitat for agriculture.

In order for informed conservation planning, information regarding a number of life history characteristics is required, including: population numbers, distribution, ecological interactions, and reproductive characters.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Classified as Data Deficient (DD) on the IUCN Red List (1).

Population

Population Trend

Major Threats

In the absence of a significant ecological study of the pygmy scaly-tailed flying squirrel, it is difficult for conservationists to properly assess how threatened it is. Nonetheless, of most concern at this stage, particularly given the dependence of these rodents on mature forests, is the effect of logging activities within its range (3) (6). Between 1990 and 2000, commercial harvesting of timber, together with land clearance for agriculture, accounted for a loss of 9.1 million hectares of land in central Africa (9). Fortunately, it is thought that the distribution of the pygmy scaly-tailed flying squirrel is probably more continuous than current data suggests and, therefore, its status may be Least Concern for the imminent future (1).

Conservation Actions

There are currently no strategies in place for the conservation of the pygmy scaly-tailed flying squirrel, or indeed for any Anomalure. However, despite commercial conflicts of interest, positive efforts are being made to protect central African forests from further degradation and loss of biodiversity. This includes the signing in 2005 by ten central African nations of the first region wide conservation treaty to protect seven percent of Congo Basin forests (10).

Scaly-tailed squirrel species will occasionally steal oil palm nuts, but they are not generally considered pest species.

Pygmy scaly-tailed flying squirrels are important members of their native ecosystems.