Lord Derbys anomalure

Anomalurus derbianus




Pteromys derbianus (Gray, 1842), Sierra Leone. One of the subspecies of A. derbianus in the Congo, is occasionally given species rank as A. fraseri. Sixteen subspecies.


English: Lord Derby's scalytail; French: Ecureuil volant de Derby; German: Gemeines Dornschanz-hornchen.


Physical characteristics vary geographically over its range, with the dorsal fur varying from gray to rich russet grizzled with silver. The subspecies, though all share the characteristic facial pattern of white snout, forehead, and cheeks, with a black band above the nose, around the eyes and back of the head. Head fur is dense and velvety, body fur long (to approximately 1 in [or 25 mm] or more) and silky. The tail is shorter than the head and body. The last half of the tail is generally black. The ears are naked and pink. There are six pairs of tail scales.


Widely distributed from western Sierra Leone to west Kenya and, more sparsely, from north Angola to northern Mozambique.


From sea level to 7,875 ft (2,400 m) in moist rainforests and seasonally dry woodlands, wherever forest provides food trees, refugia, and denning holes. Studies in the rainforests of Gabon found that most roosting trees were hollow with both basal and high holes. The high hole was often only just big enough to squeeze an anomalure body through. There was no preference in tree species.


Up to eight animals may share a den, and individuals show fidelity to a particular den for many seasons. Social behavior of A. derbianus remains to be studied. Den may be up to 130 ft (40 m) up, always in a hollow in an old tree. Used holes may vary in diameter from 1 to 8 ft (0.3-2.5 m). In the den, humidity varies little (90-95%) and temperature is also fairly constant (66-77°F [19-25°C]).

Although predominantly nocturnal, anomalures enjoy sunbathing in the early morning and, to a lesser extent, in the late afternoon. Vocalizations include a variety of social purrs and twitters and a series of defensive growls and hisses. Longdistance movement is by gliding, with speed checked before alighting by a final upturn to induce a stall. A. derbianus has been reliably measured as having glided 820 ft (250 m). An adult female, radio-tracked in a Gabonese rainforest, traveled an average of 1,770 ft (540 m) per night, with most glides being less than 328 ft (100 m). The total home range was less than 8.6 acres (3.5 ha). A male averaged 3,480 ft (1,060 m) per night and used an area of 22.8 acres (9.25 ha).


Diet consists of the bark of a dozen species of trees, leavened with fruits, flowers and nuts. Occasional insectivory also recorded. Thick bark from large limbs and the main trunk is preferred. A. derbianus will maintain several simultaneous feeding sites. At each, it will remove a single narrow strip adjacent to that from the previous night's feeding. Action at a particular site is curtailed when damage gets too extensive (beyond about 5.9 in [15 cm] wide). Feeding sites are initiated at natural bark wounds caused by growth splits and falling branches and by elephant damage. The trees are physiologically adapted to the rodent's depredations and grow replacement bark. In the rainforests of Gabon, an individual of the subspecies fraseri was found to have substantial volumes of termites in its stomach. Bark is sometimes scraped away and just the oozing phloem sap licked up while the bark is ignored. Such wounds may be revisited for the insects they attract.


Reproduction is seasonal for dry-forest subspecies, but not so for those inhabiting rainforests. Females may move to a special nursery den. Young are large and capable of coordinated movement soon after birth, but they remain in the nest until almost fully grown. After weaning, they are fed chewed-up food, brought in the cheek pouches of their parents. Females have also been observed gliding in the forest in the company of nearly full-grown young. Three animals were once observed gliding repeatedly between trees and chasing each other as if in play.


Despite its specializations, the species is widely spread enough not to be threatened. Population in Ghana are on CITES Appendix III.


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