704.

Hummelinck’s Vesper Mouse

Calomys hummelincki

French: Calomys de Hummelinck / German: Hummelinck-Vespermaus / Spanish: Raton laucha de Hummelincks

Other common names: Hummelinck's Laucha

Taxonomy. Baiomys hummelincki Husson, 1960, Klein Santa Martha, Curacao, Netherlands Antilles.

This species is monotypic.

Distribution. Extreme NE Colombia (La Guajira Department), N & C Venezuela, Aruba and Curacao Is, and isolated record from Roraima State in N Brazil.

Descriptive notes. Head—body 55-67 mm, tail 45-54 mm, ear 8-11-7 mm, hindfoot 13-4-15 mm; weight 11-19 g. Hummelinck’s Vesper Mouse is small; tail is much shorter than head-body length; dorsum is distinctly orange; venter is white; post-auricular patches are distinct; tail is weakly bicolored, pale above and white below; skull is delicate, with greatest length of skull of adults generally less than 21 mm and molar toothrow generally less than 3-3 mm.

Habitat. Grasslands on sandy or otherwise well-drained soils. In Venezuela, c.2-56% of records of Hummelinck’s Vesper Mice are from thorn forest, 2-5% from home gardens, and 95% from sandy grasslands.

Food and Feeding. Fecal analyses of Hummelinck’s Vesper Mice revealed predominantly herbivorous food preferences, although diets vary geographically from mostly seeds and other plant materials to mostly leaves, roots, and even some insect parts. Exterior of feces is slightly curved, and sometimes proximal end has a long vegetation fragment; lengths are 2-1-3-8 mm (average 3 mm), and diameters are 1-1-8 mm (average 1-2 mm).

Breeding. Two reproductive periods were noted in northern part of its distribuiton. Young Hummelinck’s Vesper Mice became more abundant in January and August indicating bimodal estrous cycle. Females had 2-5 embryos. Nests were built on the ground under rocks or flat coral stones.

Activity patterns. Hummelinck’s Vesper Mouse is terrestrial and nocturnal.

Movements, Home range and Social organization. Dispersal of Hummelinck’s Vesper Mouse is ageand gender-specific: juveniles of both sexes, on average, disperse in equal proportions. Subadult males disperse considerably longer distance (average 78 m) than subadult females (average 52 m). Sex ratio is male-biased, averaging 1-2: 1. Home range was also ageand sex-specific, larger in adult males (4100 m?*) and, in decreasing order, young females (1175 m®) and young males and adult females (both at ¢.700 m?). In general, this suggested polygynous mating system. One study showed relatively low levels of gene flow between and among populations. The Hummelinck’s Vesper Mouse is widespread but only locally common.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Nevertheless, natural savannas where Hummelinck’s Vesper Mice occur are currently under threat due to conversion from pasture to tree plantations and other forms of human activity. It is considered vulnerable in Aruba.

Bibliography. Bekker (1999), Brandao et al. (2017), Chiappero et al. (2002), Garcia et al. (1999), Goode et al. (1990), Handley (1976), Linares (1998), Martino & Capanna (2002), Martino, Capanna & Filippucci (2001), Martino, Filippucci & Capanna (2002), Ochoa, Aguilera & Rivas (2016), Pérez-Zapata et al. (1987), Salazar-Bravo (20156¢), Solari et al. (2013), Voss (1991a).