The Gambian pouch rat, Cricetomys gambianus, also known as the African Giant Pouch rat, is a nocturnal pouched rat native to Africa. It is the largest rat in the world, growing to be as big as raccoon and weighing up to 9 lbs. They have very poor eyesight and so depend a lot on their senses of smell and hearing. Their name comes from the large, hamster-like pouches they have in their cheeks. They are not true rats (subfamily Murinae), but are part of a uniquely African radiation of muroid rodents.

In their native Africa, these rats live in colonies of up to twenty strong, usually in forests and thickets, but also commonly in termite mounds. They are completely omnivorous, feeding on vegetables, insects, crabs, snails, and other items, but apparently preferring palm fruits and palm kernels.

Unlike domestic rats, they have cheek pouches like a hamster. These cheek pouches allow them to gather up several kilograms of nuts per night for storage underground. They have been known to stuff their pouches so full of date palm nuts so as to be hardly able to squeeze through the entrance of their burrows. The burrows consist of a long passage with side alleys and several chambers, one for sleeping and the others for storage.

These rats reach sexual maturity at 5-7 months of age. They have up to four litters every nine months with up to six offspring in each litter.

Male pouch rats are territorial and tend to be aggressive when they encounter one another, otherwise these rodents are extremely friendly and have become popular as exotic pets. They are intelligent, social and can be very gentle if handled from an early age.

Problems with the pouch rat

Currently these rats have been an invasive species on Grassy Key in the Florida Keys. It is unknown how the rat was released to the wild, and there is fear that if the rats reach Key Largo they could invade the Everglades and cause great ecological damage. Biologists say it would compete for food with native species, carry diseases, and damage the bird population by eating their eggs.

This outsized African rodent is also believed to be responsible for the current outbreak of monkeypox in the United States. In 2003, the United States' Centers for Disease Control and Prevention and the Food and Drug Administration issued an order preventing the importation of the rodents following the first reported outbreak of monkeypox. Several African species are believed to carry the disease.

Pouch rats as mine-sniffers

Experiments are being run in Africa using this species of rat to sniff out mines in minefields. It has a very acute sense of smell and a natural explorative behavior that makes it excellent at detecting mines. The rats are tethered to their trainers and set about searching for the hidden mines. Once the rats show the trainer they've sniffed out a mine, they receive a food reward.

References

• Novak, R.M. and Paradiso, J.L.; Walkers Mammals of the World, Vol II. Johns Hopkins University Press, Baltimore, 1991.
• [1] (http://news.yahoo.com/news?tmpl=story&u=/ap/20050103/ap_on_sc/gambian_rats_2) - a story from Yahoo news covering concerns about the rat in Florida.