523.

Huanchaca Burrowing Mouse

Juscelinomys huanchacae

French: Akodon du Huanchaca / German: Huanchaca-Maulwurfsmaus / Spanish: Ratén cavador de Huanchaca

Other common names: Huanchaca Akodont

Taxonomy. Juscelinomys huanchacae Emmons, 1999, Campamento “Huanchaca II,” Parque Nacional Noel Kempff Mercado, Santa Cruz, Bolivia.

This species is monotypic.

Distribution. E Bolivia, known only from four close localities in Noel Kempft Mercado National Park.

Descriptive notes. Head-body 130-192 mm, tail 84-100 mm, ear 17-18 mm, hindfoot 21-27 mm; weight 61-99 g. The Huanchaca Burrowing Mouse is a medium-sized, Oxymycteruslike sigmodontine, with overall color uniform olivaceous and moderate countershading. Head is prominent, with short rostrum, moderately sized eyes, and rufous eye-ring. Dorsal color is a mix of yellow and black-tipped hairs; pelage is 10-12 mm long at mid-back, with pale gray bases, darkening to blackish at mid-length, either tipped black or broadly ocherous yellow with or without narrow terminal black tip; and color of sides is similar to dorsum. Ventral pelage is uniformly gray-based, tinged with buff or pale gray; sides of muzzle are paler, washed with ocherous yellow; chin and circumoral region are whitish or yellowish; ears are well-haired inside and out with short, pale-tipped hair, rim with slight, pale fringe; hair of forefeet and hindfeet has dusky bases and white tips; and ungual tufts are silvery. Claw of central digit of manus is 5-6 mm long; claws of pes are well-developed and c¢.3 mm long. Tail is “conical” in appearance (proximal diameter c.6 mm), completely covered with stiff hairs, predominately black and contrasting with body color, and paler, washed with pale buff below, palest near base, but not conspicuously bicolored. Incipient apical tuft has hair ¢.7 mm long. There are four pairs of mammae: one pectoral, one axillary, one lower abdominal, and one inguinal. Vibrissae are short, fine, and inconspicuous; mystacial vibrissae reach behind eyes. Tail skin breaks easily and slips off at any point along its length, and many individuals have short or entirely missing tails. Study skins are extremely greasy and exude oil.

Habitat. Huanchaca or Caparuch Tableland Massif (type locality) in wet open savanna with scattered short trees at an elevation of 700 m; other specimens from well-drained grasslands interspersed with woody shrubs and trees in lowlands at the foot of the tableland (200 m).

Food and Feeding. Stomach contents of the Huanchaca Burrowing Mouse included adult ants and insect larvae, lepidopteran or coleopteran, and small amounts of plant tissue (fruits, leaf, stem, or grass seed).

Breeding. Many female Huanchaca Burrowing Mice were pregnant or lactating in early October (late dry—early rainy season). Males with enlarged testes (¢.8 mm x 14 mm) were also recorded then. Embryo numbers were 1-3. Of 22 mark-and-release females examined visually and by palpation between 21 September and 11 October,six were non-reproductive adults, four were pregnant, three lactating, one was in estrus, and six were non-parous juveniles. One male first captured as an adult survived to be recaptured in the following year.

Activity patterns. The Huanchaca Burrowing Mouse is terrestrial. It readily entered standard traps; despite its common name,its large surface movements did not indicate a fossoriallifestyle.

Movements, Home range and Social organization. In 2001, four adult male Huanchaca Burrowing Mice were captured at more than one trap site (mean recaptures 4-7), moving a mean distance of 60 m between traps (range 40-80 m), and three females (mean recaptures 4-3) moved a mean distance of 40 m (20-60 m). In 2002, five males moved a mean of 64 m (40-80 m), but the three females moved longer distances: 60 m, 120 m, and 180 m (the only one to travel from one trap line to another). In the year with most captures, the area circumscribed by all 15 traps where 15 individuals were captured was 4-9 ha, or 20% oftrap sites on ¢.35% of the plot area. The Huanchaca Burrowing Mouse was readily captured and recaptured in large Sherman live traps. Long claws may serve to dig deep nesting burrows to escape predation, savanna fires, and desiccation of months without rain and to dig for invertebrate prey. Over twelve years of trapping a standard plot, the population of Huanchaca Burrowing Mouse went through apparent extinction (no individuals captured) for three successive years, followed by partial recovery, two more years of absence, and then presence again. This time/space variability suggested that the Huanchaca Burrowing Mouse is a microhabitat specialist that is ultra-sensitive to interannual resource changes.

Status and Conservation. Classified as Data Deficient on The IUCN Red List. Currently available data for the Huanchaca Burrowing Mouse suggests that a Near Threatened classification might be a more appropriate category for its conservation status.

Bibliography. Dunnum, Emmons et al. (2008), Emmons (1999, 2009, 2015), Emmons & Patton (2012), Emmons et al. (2006), Moojen (1965).