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Rajah Sundaic Spiny Rat

Maxomys rajah

French: Maxomys raja / German: Braune Rajah-Ratte / Spanish: Rata espinosa de Sonda raja

Other common names: Brown Spiny Rat, Rajah Spiny Rat, Rajah Sundaic Maxomys

Taxonomy. Mus rajah Thomas, 1894,

“Mount Kina Balu,” northern Borneo, Malaysia.

Maxomys rajah forms a clade with M. pa-gensis, with which it is a sister species, and M. panglima. Monotypic. Distribution. S peninsular Thailand, Peninsular Malaysia, Sumatra, Borneo, and some offshore Is.

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Descriptive notes. Head-body 166- 226 mm, tail 162-210 mm, ear 21-24 mm, hindfoot 35-43 mm; weight 95-220 g. The Rajah Sundaic Spiny Rat is large and similar to the Indomalayan Spiny Rat ( M. surifer). Pelage is short and very spiny. Dorsum is brown to reddish brown or orangish brown, being darker along back and lighter along sides, with manystiff gray-brown spines. Venter is white, with dark brown streak down abdomen and many softer white spines throughout; ventral pelage is sharply demarcated from dorsal pelage.Juveniles are very dark blackish brown, fading through gray to white ventrally, and they are not identifiable to the species level. Feet are white, long, and narrow. Ears are long and dark brown; vibrissae are long and dark. Tail is 90-95% of head-body length and sharply bicolored, dark brownish black above and white below. Rostrum is long and narrower than in the Broad-nosed Sumatran Spiny Rat ( M. inflatus). Various species of mites (Laelaps sanguisugus, L. sculpturata, and Longolaelaps longutus), chiggers (Gahrlepia fletcher), and ticks (Amblyomma, Ixodes granulatus, and Haemaphysalis) have been recorded from the Rajah Sundaic Spiny Rat. There are four pairs of mammae: one pectoral, one post-axillary, and two inguinal. Chromosomal complement is 2n = 36, FN = 56.

Habitat. Primary and disturbed lowland evergreen tropical forestfrom sea level to elevations of ¢.1100 m. Rajah Sundaic Spiny Rats are rarely found in disturbed forests and oil palm plantations, which fragment their distribution in some areas.

Food and Feeding. The Rajah Sundaic Spiny Rat eats various arthropods and vegetation, including variousfruits.

Breeding. The Rajah Sundaic Spiny Rat can breed monogamously, with pairs sharing parts of their home ranges.

Activity patterns. The Rajah Sundaic Spiny Rat is nocturnal and terrestrial. It builds nests in burrows (c.2 m deep ending in nesting chamber) and rarely in cavities in logs or roots, with 1-2 entrances covered with leaflitter.

Movements, Home range and Social organization. In Borneo, home ranges were 200-1400 m? (mean 670-6 m?). Females (mean 666-7m?) had similarly sized home ranges as males (671-4 m?). Home rangesrarely overlap, but when they do,it is usually between a male and a female rather than individuals of the same sex. Home ranges of Rajah Sundaic Spiny Rats and sympatric Whitehead’s Sundaic Spiny Rats ( M. whiteheadi) overlap substantially. Populations of Rajah Sundaic Spiny Rats can very common to very rare between years, being less abundant during times of drought but more abundant than Whitehead’s Sundaic Spiny Rats in the same region. During mass fruiting events, populations of Rajah Sundaic Spiny Rats can explode.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. The Rajah Sundaic Spiny Rat has a wide distribution and is found in numerous protected areas, including Maliau Basin Conservation Area, Gunung Stong State Park, and Wang Kelian State Park. Population size is predicted to have dropped by 30% in the last ten years due to extensive deforestation. It is threatened mainly by logging and agricultural expansion.

Bibliography. Achmadi et al. (2013), Corbet & Hill (1992), Francis (2008), Jayaraj, Daud et al. (2013), Jayaraj, Tahir et al. (2012), Musser & Carleton (2005), Musser et al. (1979), Nakagawa et al. (2007), Nor (2001), Paramasvaran et al. (2009), Phillipps & Phillipps (2016), Rickart & Musser (1993), Ruedas, L.A. (2016a), Shadbolt & Ragai (2010), Steppan & Schenk (2017), Yong (1972), Wells, Lakim & Pfeiffer (2006).