Subfamily Cricetomyinae
pouched rats

Cricetomyinae, also known as pouched rats and mice, is an Old World group of nesomyid rodents. This subfamily contains eight species in three genera (Beamys, Cricetomys, and Saccostomus), divided between two tribes. (Musser and Carleton, 2005)

Cricetomyines are native to sub-sarahan Africa. (Carleton and Musser, 1984)

Cricetomyines live in savannahs, agricultural fields, sandy plains, scrub forests, moist woodlands, and forests. They are found at elevations from sea level to 2,100 meters. (Carleton and Musser, 1984; Nowak, 1999)

At first, cricetomyines were classified within the subfamily Murinae (Thomas 1896, Ellerman 1941, Simpson 1945), and Cricetomyinae was not defined as a monophyletic group until 1951 (Roberts 1951). Different authors have placed cricetomyines in the families Cricetidae (Petter 1966) and Muridae (Carleton and Musser 1984, Musser and Carleton 1993), and Chaline et al. (1977) gave the group family status. Molecular studies show that cricetomyines are most closely related to dendromurines, and that they fall within the clade given the family name Nesomyidae (Michaux et al. 2001, Jansa and Weksler 2004, Steppan et al. 2004).

Based on morphological and molecular characteristics, it seems that Saccostomus is an outgroup to the other two genera in this subfamily, Beamys and Cricetomys (Roberts 1951, Corti et al. 2004). Roberts (1951) even placed Saccostomus in its own subfamily, Saccostomurinae. Saccostomus is estimated to have diverged from the other two genera between 9 and 14 million years ago, whereas Beamys and Cricetomys diverged between six and ten million years ago (Corti et al. 2004). Recently it was discovered that Cricetomyinae may be much more diverse than originally thought, as the two recognized species of Saccostomus actually represent complexes of cryptic species that vary in their chromosome number and arrangement (Corti et al. 2004). A revision of the taxonomy of this group at the species level is therefore needed. (Carleton and Musser, 1984; Chaline, Mein, and Petter, 1977; Corti et al., 2004; Ellerman, 1941; Jansa and Weksler, 2004; Michaux, Reyes, and Catzeflis, 2001; Musser and Carleton, 1993; Petter, 1966; Roberts, 1951; Simpson, 1945; Steppan, Adkins, and Anderson, 2004; Thomas, 1896)

Cricetomyines range in length from 98 mm to 450 mm, and their tails measure 30 to 450 mm. The length of the tail is less than or equal to the length of the body. Pouched rats weigh anywhere from 40 g to almost 3 kg. Male Cricetomys are larger than female Cricetomys, but sexual dimorphism has not been reported for the other genera. Cricetomyines have robust bodies with large heads and short limbs. These rodents get their common name from their large cheek pouches. The ears are rounded and may be short or very large and nearly naked. The thick tail is naked or covered with short hairs and the eyes are relatively small. The strong hind feet have short toes. The pelage may be long and dense or short, coarse, and sleek, and it is gray or brown on the dorsal surface of the animal and white, gray, or buff-colored below. The soles of the feet are hairless.

The cricetomyine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The upper incisors are ungrooved, and the molars are rooted and cuspidate. There are accessory stylids on the labial side of the lower molars and accessory styles on the lingual side of the upper molars. The chevron-shaped enamel ridges of the molars are not joined by longitudinal mures or murids. There is a circular posteromedial cusp on the first and second lower molars. The mandibular ramus is relatively deep. The rostrum is long, and the area between the orbits is shaped like an hourglass. There is a slight notch and spine formed from the zygomatic plate. The jugal is large and composes most of the zygomatic arch. The malleus is of parallel construction. (Carleton and Musser, 1984; Nowak, 1999)

The record longevity of a pouched rat in captivity is 7 years, 10 months. Cricetomyines in the wild undoubtedly live much shorter lives. (Nowak, 1999)

Cricetomyines are nocturnal rodents, only occasionally foraging during the day. They are mainly terrestrial, but some climb and forage in trees and shrubs. On the ground, they walk with a slow, ambling gait. They build nests out of dry vegetation and place them in rock crevices, hollow trees, or in simple burrows situated among rocks. These simple burrows range from one to nine meters in length and are about 60 cm below the soil surface. Burrows contain chambers for storing food. Pouched rats have also been known to make use of burrows constructed by other animals. Cricetomyines are usually solitary, but males and females sometimes build their nests fairly close to one another. (Carleton and Musser, 1984; Nowak, 1999)

Cricetomyines communicate with one another through a range of complex vocalizations. They rely most on their senses of smell and hearing, as their eyes are fairly small, and if forced out into the daylight they behave as if nearly blind. (Carleton and Musser, 1984; Nowak, 1999)

These rodents are herbivorous or omnivorous, eating fruit, seeds, nuts, berries, roots, bulbs, crabs, snails, and sometimes insects. Coprophagy is known to occur in this group. Pouched rats hoard food in their large cheek pouches and carry it back to their burrows to store. (Carleton and Musser, 1984; Nowak, 1999)

Small mammalian carnivores, owls, snakes and humans are the most important cricetomyine predators. These animals probably rely on their vigilance, agility, and nocturnal habits to evade predation. (Carleton and Musser, 1984)

Cricetomyines have roles as primary and secondary consumers, and they are a food source for other mammals. Because of their habit of storing seeds, it is likely that cricetomyines also have a role in seed dispersal. Finally, cricetomyines are hosts for various flea species, including Xenopsylla crinita, Xenopsylla tortus, Xenopsylla sarodes, Dinopsyllus semnus, as well as a parasitic earwig, Hemimerus vosseleri, and numerous ticks. (Hubbard, 1972; Nowak, 1999)

In some cities and towns, Cricetomys gambianus has become commensal with humans, living in sewers along with Rattus where it is also considered a pest. Also, cricetomyines carry the plague in some areas. (Hubbard, 1972; Nowak, 1999)

Some native tribes hunt and eat Cricetomys gambianus, and this species is sometimes kept as a pet by rodent enthusiasts. (Nowak, 1999)

The two Beamys species are currently listed as near threatened by the IUCN, due to human-induced habitat loss and degradation. (IUCN, 2004)