703.

Drylands Vesper Mouse

Calomys musculinus

French: Calomys d/Argentine / German: Trockenland-Vespermaus / Spanish: Raton laucha de secano

Other common names: Drylands Laucha

Taxonomy. Eligmodontia laucha musculina Thomas, 1913, Maimara, 2230 m, Jujuy, Argentina.

Geographical variation in size and color is evident among populations of C. musculinus, however, several lines of evidence suggest that these may be associated with recent and extensive geographical and demographic expansion processes. Monotypic.

Distribution. CW & C Bolivia and W Paraguay to S Argentina .

Descriptive notes. Head-body 81:8-93-4 mm, tail 72-1-81 mm, ear 12:9-14-3 mm, hindfoot 16-5-17-7 mm; weight 15-1-24-4 g. Dorsum of the Drylands Vesper Mouseis sandy brown lined with black hairs to gray all over, usually with darker rumps. Venter is white, and head is about the same color as dorsum. Ears are rounded, covered internally by short, delicate brownish yellowish hairs, and contrast head with white concha and tragus. Hindfeet are long and narrow, covered with white hair. Tails are often bicolored, dark brown to black above and clear to creamy white below.

Habitat. Patagonian Pampas, “Espinal” (thorn), and Monte ecoregions of central Argentina; Yungas and Puna of northern Argentina and southern and central Bolivia; and Dry Chaco of Paraguay from sea level to elevations of ¢.3300 m.

Food and Feeding. The Drylands Vesper Mouse is omnivorous, with a preference for arthropods in spring and summer.

Breeding. Breeding season of the Drylands Vesper Mouse is highly seasonal but can be long (September—June). Extremely early ovulation at the time of weaning at c.21 days was recorded in captive females. Numbers of embryos averaged 6-1-7-5. Nests are large relative to body size and built aboveground or under shrubs and rocks.

Activity patterns. The Drylands Vesper Mouse is mainly nocturnal and crepuscular. It can tolerate not drinking free water for up to five months and can enter daily torpor to reduce energy expenditure related to maintaining constant body temperature in cold, dry environments.

Movements, Home range and Social organization. Home ranges of male Drylands Vesper Mice are larger than those of females during breeding season but about the same size during non-breeding season. Polygynous mating system has been suggested. Males were non-territorial and never exhibited aggressive behavior toward females.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Bozinovic & Rosenmann (1988b), Busch et al. (1997), Buzzio & Castro-Vazquez (2002), Carreno et al. (1990), Ellis et al. (1998), Giannoni et al. (2005), Gonnet & Ojeda (1998), Laconi & Castro-Vazquez (1999), Laconi et al. (2000), Mares (1977), Massoia et al. (1968), Mills, Ellis, McKee, Calderén et al. (1992), Mills, Ellis, McKee, Maiztegui & Childs (1991), Salazar-Bravo (2015c), Steinmann & Priotto (2011), Steinmann, Priotto, Castillo & Polop (2005), Steinmann, Priotto & Polop (2009), de Villafane et al. (1992), Yahnke (2006), Yunes et al. (1991).