628.

Shortfaced Oldfield Mouse

Thomasomys baeops

French: Thomasomys a téte courte / German: Kurzkopf-Paramomaus / Spanish: Raton de erial de cara corta

Other common names: Beady-eyed Mouse, Short-faced Thomasomys

Taxonomy. Oryzomys baeops Thomas, 1899, “Pita R[iver]., 3500 m, above the Chillo Valley, Pichincha, Ecuador. Alt. 3500 metres.”

Morphological differences occur in Ecuadorean and Colombian populations suggesting that taxonomy of 7. baeops needs additional taxonomic scrutiny. Monotypic.

Distribution. Andes of Colombia and Ecuador.

Descriptive notes. Head-body 95-120 mm, tail 106-147 mm, hindfoot 24-27 mm, ear 16-19; weight 27-45 g. Pelage of the Shortfaced Oldfield Mouse is quite long, soft, and woolly. Dorsum is dull grayish brown, darker along middle line of back, and venter is silvery gray, with light brown tone extending anteriorly to bases of mystacial vibrissae. Pelage above hands is whitish, and above hindfeet,it is pale brown with whitish digits. Mystacial vibrissae are very long and extend far behind ears when bent. Tail is unicolored or bicolored and moderately long (102-139% of head-body length). Hallux is long, with claw extending to interphalangeal joint of second digit, and fifth digit is very long, extending to base of claw of fourth digit. Females have three pairs of nipples: one postaxial pair, one abdominal, and one inguinal.

Habitat. Andean forests and paramo habitats at elevations of 1300-3800 m. The Shortfaced Oldfield Mouse lives in sections of primary/secondary cloud forest mosaics and Polylepis (Rosaceae) forests, but it prefers areas with abundant shrubby vegetation and little canopy development.

Food and Feeding. The Short-faced Oldfield Mouse eats seeds and insects. A captive individual ate small fruit from Coriaria ruscifolia ( Coriariaceae); Gaultheria glomerata and Pernettya prostrata, both Ericaceae; and Rubus nubigenus ( Rosaceae).

Breeding. In dry season (September), a lactating Short-faced Oldfield Mouse was recorded, and a female with three embryos also was captured in Sangay National Park.

Activity patterns. The Short-faced Oldfield Mouse is nocturnal.

Movements, Home range and Social organization. The Short-faced Oldfield Mouseis frequently recorded on the ground, along margins of small streams, in narrow trails through mossy debris and damp leaf litter, under mossy logs, in holes undertree roots, and on mossy branches of small trees.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Shortfaced Oldfield Mouse has a wide distribution and presumably large overall population. It seems to be tolerant of habitat modification. In Colombia and Peru, it may be rare.

Bibliography. Barnett (1999), Brito, Teska & Ojala-Barbour (2015), Jarrin (2001), Lee et al. (2011), Pacheco (2003, 2015b, 2016b), Salazar-Bravo & Yates (2007), Thomas (1899b), Tirira (2007), Voss (2003).