Bibimys chacoensis
chaco crimson-nosed rat

Chaco crimson-nosed rats are native to the Neotropical region and can be found in the province of Misiones in northeastern Argentina and in southeastern Paraguay. (D'Elia and Pardinas, 2008)

Bibimys chacoensis lives in wet regions of the Chaco grasslands in northeastern Argentina and in southeastern Paraguay. They generally live around 125 m of elevation but are not found above 300 m. (D'Elia and Pardinas, 2008; Eisenberg and Redford, 1999; Webb, et al., 2010)

Chaco crimson-nosed rats are members of the subfamily Sigmodontinae, which have a dental formula of 1/1, 0/0, 0/0, 3/3, for a total of 16 teeth. This species has short ears, a short tail, and enlarged claws. Like other members of Bibimys, B. chacoensis can has a crimson nose. Lateral pelage of the torso tends to have a buffy appearance and is dark along the dorsal surface of the body. Ventral pelage is whitish and slight buffy in appearance. On average, chaco crimson-nosed rats weigh 28.6 g and have a total body length of 162.9 mm. Tail length ranges from 35 mm to 81 mm, with an average of 66.14 mm. Hind foot length (including the claw) averages 21.9 mm and ranges from 20 to 25 mm. Ear length averages 16.3 mm and ranges from 16 mm to 18 mm. The number of roots of the third molar can be used to distinguish Chaco crimson-nosed rats from other members of the genus Bibimys. Chaco crimson-nosed rats have 3 roots, while most other members of Bibimys have only 2. (D'Elia, et al., 2008; Eisenberg and Redford, 1999)

Currently, there is no information available on the mating system of Bibimys chacoensis.

Little information is available on the reproductive behavior of Bibimys chacoensis. Members of the genus Akodon, close relatives to Bibimys, typically have breeding seasons extending from August to May but may vary according to climate and resource availability. Litters consist of 3 to 4 young and there are usually 2 litters per year. In one species of Akodon, Akodon azarae, implantation may be delayed and gestation last 22.7 days on average. (Nowak, 1999)

Little is know of parental care in Bibimys chacoensis. As mammals, females nurse and care for their young until weaning is complete. Akodon azarae, a member of the closely related genus Akodon, weans its young by 14 to 15 days old. (Nowak, 1999)

The chaco crimson-nosed rat's lifespan has not been documented.

The general behavior of this species has not been thoroughly studied. However, it is known that Bibimys chacoensis is fossorial. Members of the related genus Akodon can be diurnal, nocturnal, crepuscular, or active at any time. Members of the closely related genus Akodon typically dig small burrows that end in globular nests. (Eisenberg and Redford, 1999; Nowak, 1999)

Very little is known about the home range of chaco crimson-nosed rats. A closely related species, Akodon cursor, is most active within 30 m of its burrow. (Nowak, 1999)

Communication in Bibimys chacoensis is not well understood. Other sigmodontine rodents perceive their environment using vision, hearing, touch, smell, and taste. Sigmodontines primarily use auditory or chemical cues for communication with conspecifics. (Nowak, 1999)

There is insufficient information on the feeding habits of Bibimys chacoensis. However, stomach content analysis of both Akodon cursor and Akodon boliviensis, close relatives of Bibimys chacoensis, show that typical Akodon diet consists of plant material, seeds, and insects. The stomach contents of A. azarae is 25% plant matter and 75% invertebrates. (Eisenberg and Redford, 1999; Nowak, 1999)

The only documented predator of this species is the white-tailed hawk (Buteo albicaudatus), however other raptors and carnivores likely prey on this species as well. The small size of Bibimys chacoensis and its fossorial behavior help protect it from predators. Its brown pelage likely helps camouflage it from potential predators. (Eisenberg and Redford, 1999)

Although little information is available on the diet of Bibimys chacoensis, this species likely consumes insects and may help control insect pest species. As a small rodent, this species likely consumes various types of seeds and may be an important seed disperser for various plants throughout its native range. Due to its fossorial lifestyle, B. chacoensis helps aerate soil and increases water penetration into the soil. Although little information is available on potential endo- and ectoparasites specific to this species, Bibimys chacoensis is known to host a recently discovered species of sucking lice, Hoplopleura aitkeni. (Pardinas, et al., 2005)

There is no information on the potential positive effects of Bibimys chacoensis on humans.

There is no information on the potential negative impacts of Bibimys chacoensis on humans.

Although Bibimys chacoensis lives in a confined region of Argentina and Paraguay, this species is listed as "least concern" by the IUCN Red List of Threatened Species and is not protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). (D'Elia and Pardinas, 2008)

The genus Bibimys is very diverse and poorly understood. Trapping members of this genus is difficult and for that reason, many specimens are very old and badly preserved. Currently, there are only three species of Bibimys, however, the validity of the three species, Bibimys chacoensis, Bibimys labiosus, and Bibimys torresi, has not been researched extensively. (Pardinas, et al., 2005)