Overview

Distribution

Range Description

This very widespread species occurs from the coast of West Africa through central Africa to the coast of East Africa, southwards to the north-eastern tip of South Africa and southern Angola. It occurs from sea level to 2,000 m asl.
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Geographic Range

Gambian rats are found in central Africa, in regions south of the Sahara desert as far south as Zululand. This includes countries such as Nigeria among others.

Biogeographic Regions: ethiopian (Native )

  • Ajayi, S., O. Tewe, E. Faturoti. 1978. Behavioral changes in African giant rat (Cricetomys gambianus Waterhouse) under domestication. East African Wildlife Journal, 16(2): 137-143.
  • Kingdon, J. 1989. East African Mammals. London, New York: Academic Press.
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Physical Description

Morphology

Physical Description

Gambian rats are similar in size to the other species of giant pouched rat, African giant pouched rats, and are often confused with this species. Gambian rats have coarse, brown fur and a dark ring around the eyes, in contrast to African giant pouched rats, which have soft, grey coats with white fur on the belly. Their long tails are scaly and they have narrow heads with small eyes. The main physical characteristic of Gambian rats and all Cricetomys in general are their large cheek pouches. These pouches can expand to a great size, allowing Gambian rats to transport massive quantities of food if necessary. Cheek pouches also exist in other families of rodentia, such as the African hamster and members of the subfamily Cricetinae. Males and females are usually the same size, with little sexual dimorphism. Gambian rats can reach sizes up to 910 mm and beyond, including the tail. These rats also have a very low fat content, which may be the cause of their succeptibility to cold.

Range mass: 1 to 1.47 kg.

Range length: 645 to 910 mm.

Average basal metabolic rate: 71 cm^3 oxygen/hour.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 6.024 W.

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Type Information

Type for Cricetomys ansorgei
Catalog Number: USNM 181804
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): E. Heller
Year Collected: 1911
Locality: Mount Gargues (Uaragess), North Creek, Mathews Range, Rift Valley, Kenya, Africa
Elevation (m): 1829
  • Type: Heller, E. 1912 Jul 05. Smithsonian Miscellaneous Collections. 59 (16): 15.
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Type for Cricetomys ansorgei
Catalog Number: USNM 181806
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Aged
Preparation: Skin; Skull
Collector(s): E. Heller
Year Collected: 1911
Locality: Mazeras, Coast Province, Kenya, Africa
  • Type: Heller, E. 1912 Jul 05. Smithsonian Miscellaneous Collections. 59 (16): 16.
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Type for Cricetomys ansorgei
Catalog Number: USNM 181805
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Female; Adult
Preparation: Skin; Skull
Collector(s): E. Heller
Year Collected: 1911
Locality: Mount Umengo, summit, Taita Mountains, Coast Province, Kenya, Africa
Elevation (m): 1524
  • Type: Heller, E. 1912 Jul 05. Smithsonian Miscellaneous Collections. 59 (16): 16.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
The species occurs in various habitats including forest and woodland, as well as farmland, cropland, plantations and rural areas. It is considered to be an adaptable species that is even known to invade sewers.

Systems
  • Terrestrial
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Gambian rats inhabit a variety of habitats ranging from arid areas to temperate areas, but need some form of shelter to survive. Therefore, they are not usually found in completely open areas, but in areas with cover from hollow trees, rock outcroppings, or burrows made by other animals. They are occasionally known to venture into urban areas and can become pest animals.

Range elevation: 3500 (high) m.

Habitat Regions: terrestrial

Terrestrial Biomes: savanna or grassland ; forest ; mountains

Other Habitat Features: urban ; agricultural

  • Ajayi, S. 1977. Field observations on the African giant rat Cricetomys gambianus in southern Nigeria. East African Wildlife Journal, 15(3): 191-198.
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Trophic Strategy

Food Habits

Gambian rats are hoarders, and carry as much food as they can fit inside the pouches located on the inner cheeks. They are omnivores and feed on a variety of fruits, vegetables, nuts, and even insects when available. Some common foods include cassava, beans, sweet potatoes, and other roots. Termites have been known to be eaten along with snails.

Animal Foods: insects; mollusks

Plant Foods: roots and tubers; seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: omnivore

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Associations

Ecosystem Roles

Gambian rats serve to keep insect populations under control, but also act as transporters of seeds from different plants when they eat the fruits produced. Several parasitic worms inhabit the gastrointenstinal tracts of these rats, but the most prevelant of these are the Strongyloides. A study performed also showed minor prescences of tape worms among other parasites. Other parasites include Xenopsylla cheopis, Aspicularis tetraptera, Ixodes rasus, and Ornithonyssus bacoti. Hymenolepis is usually found in the small intestine while Aspicularis is found in the rectum and colon.

Ecosystem Impact: disperses seeds

  • Bobe, L., M. Mabela. 1997. Incidence of four gastro-intestinal parasite worms in group of cricetomas, Cricetomys gambianus (Rodent: Cricetidae), caught it Lukaya- Democratic Republic of Congo. Tropicultura, 15(3): 132-135.
  • Dipeolu, O., S. Ajayi. 1976. Parasites of theAfrican giant rat Cricetomys gambianus in Ibadan Nigeria. East African Wildlife Journal, 14(1): 85-89.
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Predation

There are no true predators in the wild that target Gambian rats. Although a few instances have been recorded where a bird of prey or another predator has eaten Gambian rats, they usually band together and are formidable opponents against potential predators. The biggest predator of Gambian rats is humans, the indigenous African population. These rats are considered a delicacy and are often hunted for food.

Known Predators:

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Life History and Behavior

Behavior

Communication and Perception

Gambian rats use screeching as the main form of communication. Gambian rats emit one single short cry which is distinguishable from the longer, varied pitch of African giant pouched rats. Males also use olfactory cues during courtship when they sniff the urine left by female Gambian rats.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

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Life Expectancy

Lifespan/Longevity

Gambian rats live for about 5 to 7 years in captivity, although some have been known to live as long as 8 years. Life expectancy in the wild is hard to document because of the small size of these creatures and because they are hunted so often by indigenous people.

Typical lifespan

Status: captivity:
5 to 7 years.

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Lifespan, longevity, and ageing

Maximum longevity: 8.4 years (captivity)
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Reproduction

Mating in Gambian rats involves the formation of a social pair-bond between one male and one female. The male usually sniffs or licks the urogenital areas of the female before attempting to mount the female. Gambian rats also display peculiar courtship behaviors. The male and female often stand upright and scratch one another, then chase each other until the female is ready for copulation. If the female is not receptive or rejects the male, she bites the male on the tail and back among other areas before courtship behaviors begin.

Mating System: monogamous

Gambian rats are seasonal breeders, usually breeding in the summer. The estrous cycle lasts between 3 and 15 days, while the length of estrus ranges from about 1.4 to 7.8 days. Interestingly, the estrous cycle is often irregular and seems dependent upon many external factors, the environment being one. Other factors include the presence of males, and captivity. Females reach sexual maturity at about 6 months and will typically have about 9 litters annually. The gestation period is approximately 30 to 32 days. Females are also very aggressive when giving birth to a litter.

Breeding interval: Gambian rats breed seasonally

Breeding season: Breeding usually occurs in the summer

Range number of offspring: 1 to 5.

Range gestation period: 30 to 32 days.

Average weaning age: 28 days.

Average time to independence: 30 days.

Average age at sexual or reproductive maturity (female): 6 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 25.7 g.

Average number of offspring: 3.5.

Average age at sexual or reproductive maturity (female)

Sex: female:
158 days.

Gambian rat young are born hairless, with eyes and ears closed. The characteristic long tail does not show substantial growth until about 30 to 35 days. The eyes do not open until about 21 days into development, although the young are completely covered with fur and have open ears at about 14 days. The female provides the most parental care, both as a source of warmth for the naked young and as a source of milk. The female also changes her food preference before the young are weaned, choosing softer foods. The male, on the other hand, shows almost no care to the young. It shows tolerance at best, and will sometimes kill it's young and eat them. This is not seen as often in females. An interesting form of altruism exists amongst females, where a female with a separate litter may take care of a motherless litter.

Parental Investment: altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Cricetomys gambianus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
van der Straeten, E., Kerbis Peterhans, J., Howell, K. & Oguge, N.

Reviewer/s
Amori, G. (Small Nonvolant Mammal Red List Authority) & Cox, N. (Global Mammal Assessment Team)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, presumed large population, it occurs in a number of protected areas, has a tolerance of a degree of habitat modification, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

History
  • 2004
    Least Concern
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Gambian rats are in danger of being overhunted, but due to their rapid generation time the population has not reached the levels of critically endangered or otherwise.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

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Population

Population
It is an abundant species.

Population Trend
Stable
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Threats

Major Threats
There are no major threats to this adaptable species. It is eaten throughout its range but it is such an abundant species that harvesting is not considered to be a major threat. The species is also used in medical research and has been recorded in the European pet trade. It is considered to be a species pest in some areas.
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Management

Conservation Actions

Conservation Actions
The species occurs in several protected areas. Research into taxonomy is needed.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Gambian rats are sometimes considered pests in urban areas where they may infest the sewers. In rural areas, they may destroy farm crops and build burrows in the soil which lead to soil desiccation and loss of plant crops. Gambian rats often inhabit barns and other farm buildings which can lead to property damage.

Negative Impacts: crop pest

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Economic Importance for Humans: Positive

The biggest economic impact of Gambian rats is as a source of food in Africa. They are considered rather tasty and are hunted and even raised on farms for their meat. This had led to a significant drop in the population. A smaller industry is the pet industry, although these rats are rather large and sensitive to temperature changes, resulting in a need for high maintenance. In the scientific community, these rats are often used for experiments, and these rats provide a wealth of information on rodent physiology and behavior.

Positive Impacts: pet trade ; food

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Wikipedia

Gambian pouched rat

The Gambian pouched rat (Cricetomys gambianus), also known as the African giant pouched rat, is a nocturnal pouched rat of the giant pouched rat genus Cricetomys. It is among the largest muroids in the world, growing up to about 0.9 metres (3 ft) long including their tail which makes up half their length.[2] It is widespread in Sub-Saharan Africa, ranging geographically from Senegal to Kenya and from Angola to Mozambique (although it is absent from much of the DR Congo, where Emin's pouched rat is present) and in altitude from sea level to 2,000 metres (6,600 ft).[1]

Characteristics[edit]

The Gambian pouched rat has very poor eyesight and so depends on its senses of smell and hearing. Its name comes from the large, hamster-like pouches in its cheeks. It is not a true rat but is part of a uniquely African branch of muroid rodents. It typically weighs between 1 and 1.4 kilograms (2.2 and 3.1 lb).[2] In its native Africa, this pouched rat lives in colonies of up to twenty, usually in forests and thickets, but also commonly in termite mounds. It is omnivorous, feeding on vegetables, insects, crabs, snails, and other items, but apparently preferring palm fruits and palm kernels.

Unlike domestic rats, it has cheek pouches like a hamster. These cheek pouches allow it to gather up several kilograms of nuts per night for storage underground. It has been known to stuff its pouches so full of date palm nuts so as to be hardly able to squeeze through the entrance of its burrow. The burrow consists of a long passage with side alleys and several chambers, one for sleeping and the others for storage. The Gambian pouched rat reaches sexual maturity at 5–7 months of age. It has up to four litters every nine months, with up to six offspring in each litter. Males are territorial and tend to be aggressive when they encounter one another.

Cases of attacks on humans[edit]

Some cases of deadly attacks against human babies have been recorded in South Africa.[3]

Invasive species[edit]

A Gambian pouched rat caught in the Florida Keys

Gambian pouched rats have become an invasive species on Grassy Key in the Florida Keys,[4] after a private breeder allowed the animals to escape.[5] This outsized African rodent is also believed to be responsible for the current outbreak of monkeypox in the United States, after spreading it to prairie dogs which were purchased as pets. In 2003, the United States' CDC and FDA issued an order preventing the importation of the rodents following the first reported outbreak of monkeypox. Around 20 individuals were affected.[6]

Ability to detect land mines and tuberculosis by scent[edit]

Main article: APOPO

A Tanzanian social enterprise founded by two Belgians called APOPO, trains Gambian pouched rats to detect land mines and tuberculosis with their highly developed sense of smell. The trained pouched rats are called HeroRATS.

Currently studies are being conducted in the USA and other locations about the best ways to train these creatures and their abilities/limits to detecting the mines

See also[edit]

References[edit]

  1. ^ a b van der Straeten, E., Kerbis Peterhans, J., Howell, K. & Oguge, N. (2008). "Cricetomys gambianus". IUCN Red List of Threatened Species. Version 2009.1. International Union for Conservation of Nature. Retrieved 11 July 2009. 
  2. ^ a b Kingdon, J. (1997). The Kingdon Field Guide to African Mammals. p. 199-200. ISBN 0-12-408355-2
  3. ^ "Giant Rats Viciously Kill, Eat Babies", International Business Times 
  4. ^ "More huge Gambian rats found on Grassy Key", keysnet.com, March 25, 2012 
  5. ^ Florida tries to wipe out cat-sized African rats, Reuters, 2007 
  6. ^ Conlon, Michael (2008-10-06). "Kids want an exotic pet? Ask your doctor first". Reuters. Retrieved 2008-10-06. 
  • Novak, R.M. and Paradiso, J.L.; Walkers Mammals of the World, Vol II. Johns Hopkins University Press, Baltimore, 1991.
  • Perry, N. D., et al. 2006. "New invasive species in southern Florida: Gambian rat (Cricetomys gambianus)". Journal of Mammalogy, 87:262-264.
  • Peterson, A. T., et al. 2006. "Native range ecology and invasive potential of Cricetomys in North America". Journal of Mammalogy, 87:427-432.
  • [1] - a story from National Geographic News regarding the use of giant pouched rats and bees to detect land mines in Africa
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