464.

Lund’s Water Rat

Lundomys molitor

French: Oryzomys de Lund / German: Lund-Wasserratte / Spanish: Rata de agua de Lund

Other common names: Greater Marsh Rat, Lund’s Amphibious Rat

Taxonomy. Hesperomys molitor Winge, 1887, cave chamber (Lapa da Escrivania Nr. 5) near Lagoa Santa, Minas Gerais, Brazil.

Lundomys molitor is the type species of the genus. Uruguayan populations have been allocated to a subspecies magnus, but validity of subspecific classification is pending. Monotypic.

Distribution. S Brazil (Rio Grande do Sul State) and Uruguay.

Descriptive notes. Head-body 170-242 mm, tail 190-289 mm, ear 23-27 mm, hindfoot 60-68 mm; weight 250-490 g. Lund’s Water Rat is one of the largest sigmodontines, with long, dense, soft, yellowish brown dorsal pelage and buffy under parts. Ears are small, rounded, and well-covered with short brownish or yellowish hair. Mystacial vibrissae are short. Hindfoot is huge for a sigmodontine, with naked claws (length c.4-5 mm), conspicuous interdigital webbing, and dense fringes of long silvery hairs along plantar margins; plantar surface is hairless and densely squamate, with small pads. There are four pairs of mammae in inguinal, abdominal, postaxial, and pectoral locations. Sparsely haired tail is unicolored and much longer than head-body langth and has a perceptible lateral compression. Chromosomal complement is 2n = 52, FN = 58.

Habitat. Freshwater marshes, ponds, and streams bordered by grass, brush, and gallery forests in temperate and subtropical environments.

Food and Feeding. Lund’s Water Rate is supposedly herbivorous but more likely om-NIvOrous.

Breeding. Lund’s Water Rat breeds from spring to autumn (September—May). Onefemale captured in early April had three embryos, each c.12 mm crown-rump. It builds elaborate spherical nests supported by and constructed from reeds, placed ¢.80 cm above water.

Activity patterns. Lund’s Water Rat is nocturnal. The species is semi-aquatic and probably the most adapted oryzomyine to life in water. It builds nests in reeds above water.

Movements, Home range and Social organization. Lund’s Water Rat is not abundant and difficult to locate.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Nevertheless, Lund’s Water Rat has suffered regional extinctions during Quaternary times; type locality is ¢.10° N the nearest known living population.

Bibliography. Barlow (1969), Freitas, Mattevi, Oliveira, Souza et al. (1983), Gonzalez & Martinez (2010), Gonzélez et al. (2016), Marques (1988), Massoia (1976), Sierra de Soriano (1965, 1969), Teta & Pardinas (2006), Voss (2015c¢), Voss & Carleton (1993).