330.

Isabel Island Giant Rat

Solomys sapientis

French: Solomys de Santa Isabel / German: Santa-Isabel-Nacktschwanzratte / Spanish: Rata gigante de Isabel

Other common names: Isabel Giant Rat, Isabel IslandSolomys, Isabel Naked-tailed Rat

Taxonomy. Uromys sapientis Thomas, 1902,

Santa Isabel, Solomon Islands.

Solomys sapientis is the type species of genus. In the past it has been included at various times in Melomys and Uromys . G. G. Musser and M. D. Carleton in 2005 placed Solomys, together with Uromys, Melomys, Protochromys, and Paramelomys, into a Uromys division. Phylogenetic study by L. M. Bryant and colleagues in 2011 found that Melomys is paraphyletic with respect to

Solomys, suggesting that taxonomic distinction of latter may require revision. Further studies are needed in order to resolve the true relationship of Solomys to Melomys of New Guinea, and an undescribed genus from New Britain. S. sapientis is possibly a recently evolved species, having probably diverged from its sister-species, S. salebrosus, c.14,000 years ago. Monotypic.

Distribution. Santa Isabel I, Solomon Is.

Descriptive notes. Head-body 188-250 mm,tail 190-257 mm, ear 17-5-19 mm, hindfoot 50-67 mm. No specific data are available for body weight. This medium-sized rat is larger than most Solomys species. Fur is close and coarse (12-15 mm), with somewhat longer guard hairs (20-23 mm) on back. Like other Solomys, it has a naked, prehensile tail, which is about as long as head-body length; basal part is haired, like the body, and distal part is completely naked, with non-overlapping scales (about 8-9 per centimeter), which is a feature of all Uromyini rodents. Upperparts are cinnamon brown, and sides and underparts are pinkish buffy; forefeet and hindfeet are gray white. Females have four mammae. Chromosomal complement is FN = 52.

Habitat. Tropical moist forest. Collected at elevations of 30 m.

Food and Feeding. E. L.. G. Troughton in 1936 reported that the Isabel Island Giant Rat cracks the ngali ( Canarium, Burseraceae) nuts and gnaws coconuts, and is found in trees felled by the natives.

Breeding. Nests are built from leaves and sticks inside hollow branches, offering some protection from predators.

Activity patterns. The Isabel Island Giant Rat is reportedly arboreal, and may rely on large forest trees for nesting sites.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Endangered on The IUCN Red List because its extent of occurrence is less than 5000 km?, its distribution is severely fragmented, and there is continuing decline in the extent and quality of its habitat owing to logging operations. It is threatened by deforestation for timber and conversion of land to cultivated use, and to some degree also by hunting for food by local people. The most

significant threat to this speciesis habitat loss, due mainly to commercial logging and the creation of farmland. It is thought that the Isabel Island Giant Rat once inhabited also nearby Malaita I and possibly San Cristobal I, but is now extinct on both. Its present range covers most of Santa Isabel, butit is becoming scarcer in the south-west of the island.

Bibliography. Aplin & Helgen (2010), Bryant et al. (2011), Ellerman (1941), Fabre, Hautier, Dimitrov & Douzery (2012), Fabre, Hautier & Douzery (2015), Flannery (1995a), Flannery & Wickler (1990), Helgen, Leary & Wright (2016e), Laurie & Hill (1954), Musser & Carleton (2005), Nowak (1999), Rimmler (1938), Tate (1951), Thomas (1902f), Troughton (19364).