Naked-tailed voalavo, Voalavo
The northern voalavo (Voalavo gymnocaudus ), also known as the naked-tailed voalavo or simply the voalavo, is a rodent in the family Nesomyidae found in the highlands of northern Madagascar. Discovered in 1994 and formally described in 1998, it is the type species of the genus Voalavo ; its closest relative is the eastern voalavo of the Central Highlands. DNA sequencing suggests that it may be more closely related to Grandidier's tufted-tailed rat than to other species of the closely related genus Eliurus. The northern voalavo is found at 1,250 to 1,950 m (4,100 to 6,400 ft) above sea level in montane wet and dry forests in the Marojejy and Anjanaharibe-Sud massifs. Nocturnal and solitary, it lives mainly on the ground, but it can climb and probably eats plant matter. Despite having a small range, the species is classified as being of least concern because it lacks obvious threats and much of its range is within protected areas.
The northern voalavo is a small, mouse-like rodent with soft, grey fur that is only slightly darker above than below. The ears are short and rounded. The long tail appears mostly naked and lacks a distinct tuft, which is present in Eliurus. It differs from the eastern voalavo mainly in the values of some measurements. The skull is delicate, with a long, narrow rostrum (front part), narrow interorbital region (between the eyes), and no development of ridges on the braincase. The molars are relatively high-crowned (hypsodont). It has a body mass of 17 to 25.5 g (0.60 to 0.90 oz).
The northern voalavo has been found only in two massifs of the Northern Highlands, Anjanaharibe-Sud and Marojejy, but may range more widely. At Anjanaharibe-Sud, the species has been found in wet mountain forest at 1,950 m (6,400 ft), where it occurred with the indigenous rodents Major's tufted-tailed rat and island mouse as well as the introduced black rat (Rattus rattus ), and in drier forest at about 1,300 m (4,300 ft), where it may live alongside other species of Eliurus and Voalavoanala. The Marojejy records come from similar habitats at 1,250 to 1,875 m (4,101 to 6,152 ft) above sea level.The northern voalavo probably largely lives on the ground, but is able to climb in vegetation. It likes areas with dense networks of roots, among which it moves using runways and natural tunnels. The species is nocturnal (active during the night), is solitary, probably eats fruits and seeds, and bears up to three young per litter.A variety of parasitic arthropods have been recorded on northern voalavo: mites from the families Laelapidae and Trombiculidae (both Marojejy and Anjanaharibe-Sud), the demodecid mite Demodex (Marojejy only), the atopomelid mite Listrophoroides (both Marojejy and Anjanaharibe-Sud), and unidentified sucking lice (Anjanaharibe-Sud only). In 2007, a laelapid mite found on V. gymnocaudus in Anjanaharibe-Sud was described as a new species, Andreacarus voalavo. The apicomplexan parasite Eimeria has also been recorded in Anjanaharibe-Sud.
Although it has a small range and is uncommon even within that range, no major threats are known and virtually all of its distribution is within protected areas. The species is therefore classified as "Least Concern" on the IUCN Red List.
