510.

Chacoan Pink-lipped Mouse

Bibimys chacoensis

French: Bibimys du Chaco / German: Chaco-Pinknasenmaus / Spanish: Ratén de labios rosados del Chaco

Other common names: Chacoan Akodont, Chacoan Swollen-nosed Mouse, Chaco Crimson-nosed Rat

Taxonomy. Akodon chacoensis Shamel, 1931, Las Palmas, Chaco, Argentina.

This species is monotypic.

Distribution. SE Paraguay and NE Argentina .

Descriptive notes. Head-body 95-100 mm, tail 70-75 mm, ear 14-17-7 mm, hindfoot 20-8-22-5 mm; weight 32-36 ¢. The Chacoan Pink-lipped Mouseis slightly smaller than the Lagoa Santa Pink-lipped Mouse ( B. labiosus). Overall color is olivaceous, with some buff around eyes and on sides of head and flanks; underparts are whitish, with buffy tinge; and feet appear dark brown (foreclaws c.2:6 mm). Compared with Torres’s Pink-lipped Mouse (B. forrest), the Chacoan Pink-lipped Mouse is smaller and has a more whitish venter. Four mammae occur in inguinal position; an unpaired nipple sided to the vagina was noted on one trapped adult Chacoan female—an unusual condition among cricetids.

Habitat. Flooded grasslands, palm savannas, and typically unforested formations called “campos and malezales” from humid Chaco to northern Campos ecoregions and large wetlands (Ibera and Neembucti) associated to the Parana River Basin. Paraguayan specimens of the Chacoan Pink-lipped Mouse were secured in small patches of humid grassland near or within remnants of evergreen forest.

Food and Feeding. No information.

Breeding. Four male Chacoan Pink-lipped Mice collected in July-September had scrotal testes. One female caught in January had a closed vagina, and another caughtin November was lactating and had an open vagina.

Activity patterns. The Chacoan Pink-lipped Mouse is moderately preyed on by nocturnal owls, and therefore it is probably active during the night. It has been reported as fossorial or semi-fossorial, but characterization has no empirical evidence, at least from observed behavior. A direct observation of one wild individual indicated marked activity searching the ground and digging, apparently looking for food. This behavior can be connected with the well-developed rostral tip. Most of the area occupied by the Chacoan Pink-lipped Mouse, at least in Chacoan Argentine,is under periodic flooding and appears unsuitable for a fossorial rodent.

Movements, Home range and Social organization. No information.

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

Bibliography. Castro & Gonzalez (2003), Contreras (1984), D'Elia, Mora et al. (2008), D’Elia, Pardinas & Myers (2005), Massoia (1980a, 1983, 1988), Massoia, Chebez & Heinonen (1988, 1989a, 1989b, 1989¢c, 1989d), Pardinas et al. (2017), Shamel (1931).