252.

Northern Baja Deermouse

Peromyscus fraterculus

French: Péromyscus de San Diego / German: Nordliche Baja-Hirschmaus / Spanish: Raton ciervo de Baja California septentrional

Taxonomy. Vesperimus fraterculus G. S. Miller, 1892, Dulzura, San Diego County, California, USA .

Recent studies identified P. fraterculus as a species separate from PF. eremicus, with P. fraterculus distributed on west side of the Colorado River and P. eremicus on east side of the river. Peromyscus fraterculus is in the eremicus species group. Allocation of subspecies is somewhat unclear. Monotypic.

Distribution. SW California, USA, and Baja California and NW Baja California Sur, Mexico.

Descriptive notes. Head—body 77-100 mm, tail 92-118 mm, ear 13-18 mm, hindfoot 18-22 mm; weight 13-18 g. The Northern Baja Deermouse is small to medium-sized, with ocherous to cinnamon dorsal pelage, mixed with lighter hair at tips. Head and sides are grayish, and venter is whitish. Overall, pelage is short, soft, and silky. Tailis longer than head-body length and slightly bicolored, dark above and lighter below. Soles of hindfeet are completely naked. Females are notably larger and heavier than males. Morphologically, the Northern Baja Deermouse is very difficult to distinguish from the Cactus Deermouse (PF. eremicus).

Habitat. Desert scrubland, coastal scrubland (Mediterranean), and coniferous forests from sea level to elevations of ¢.2300 m.

Food and Feeding. Northern Baja Deermice are thought to feed on flowers, fruits, seeds, buds, insects, and occasionally small lizards. They do not drink water but rely on food items for metabolic water.

Breeding. Northern Baja Deermice can reproduce year-round if resources are available, with peak generally in April-October. Gestation is c.21 days. Litters have 4-8 young, with 1-3 litters/year, on average.

Activity patterns. The Northern Baja Deermouse is nocturnal and can be semi-arboreal because it is commonly seen climbing trees or shrubs. It often burrows under rocks and roots and occasionally occupies abandoned burrows of other mammals such as woodrats ( Neotoma spp.). When temperatures are extremely high in summer, it might estivate.

Movements, Home range and Social organization. No information.

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

Bibliography. Avise et al. (1974), Brylski (1990a), Ceballos (2014c), Hall (1981), Hoffmeister (1986), Jameson & Peeters (1988), Musser & Carleton (2005), Riddle, Hafner & Alexander (2000), Veal & Caire (1979), Walpole et al. (1997).