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18
Giant Rat
The giant rat, also known as the pouched rat, is one
of Africa's largest rodents. Two species have been
distinguished: Cricetomys gambianus, which lives
chiefly in savannas and around the edges of forests
and human settlements; and Cricetomys emini, which
occurs mainly in rainforests. Both are highly prized
as food.
These animals are solitary, but they are easy to handle, have a gentle
nature, and make good pets. Researchers at the University of Ibadan
in Nigeria have been developing techniques for managing them in
captivity. Breeding stocks were established in 1973, and since then so
many generations have been bred that this small population is consid-
ered domesticated. Commercial-scale giant rat farming is now being
established in southern Nigeria.
This is a promising development because giant rats are a common
"bushmeat" throughout much of Africa. Since these herbivores are
well known there, and are acceptable as food, they may have as much
or more potential as meat animals than the introduced rabbits that are
getting considerable attention (see page 178~.
AREA OF POTENTIAL USE
The intertropical zone of Africa from the southern Sahara to the
northern Transvaal.
APPEARANCE AND SIZE
This species is among the most striking of all African rodents.
' Only the brush-tailed porcupine, the springhare (see page 278), and the grasscutter
(see next chapter) are larger.
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MICROLIVESTOCK
Because of its large size, it often causes amazement-even alarm-
when seen for the first time. The body measures as much as 40 cm,
and, on average, weighs about 1-1.5 kg. The record for a hand-reared
specimen is 1.6 kg.2
Apart from its size, the best known species (Cricetomys gambianus)
is noted for the dark hair around its eyes, a nose that is sharply divided
into dark upper and pale lower regions, and a tail that has a dark
(proximal) section and pale (distal) section. The overall body color is
a dusky gray.
The lesser known species (Cricetomys emini) has short, thin, and
relatively sleek fur. Its upper parts are pale brown; the belly is white.
DISTRIBUTION
Giant rats are commonly found from Senegal to Sudan, and as far
south as the northern region of South Africa. The main species is
mostly found in moist savannas, patches of forests, and rainforests.
However, it can also be found in all West African vegetation zones
from the semiarid Sahel to the coast. It also exists at high altitudes-
up to about 2,000 m in West Africa and 3,000 m in eastern Africa.
The rainforest species occurs in the great equatorial forest belts of
Zaire and neighboring Central African countries.
STATUS
These animals are probably not threatened with extinction. However,
they have been exterminated in some areas (such as in parts of eastern
Zaire) where the human population is dense, the land fully cultivated,
and the wildlife overhunted. Although common, they are not as well
known as one might suppose from their bulk and from the fact that
they are sometimes found around, and even inside, houses.
HABITAT AND ENVIRONMENT
Giant rats occur largely in lightly wooded dryland regions or in
forested humid regions. They cannot tolerate high temperatures or
truly arid conditions. They often live in farm areas and in gardens.
Their burrows are commonly found inside deserted termite mounds
and at the base of trees. Some have also been found in the middle of
cassava fields.
2 Information from M. Malekani.
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GIANT RAT
J
The giant rat's native distribution.
BIOLOGY
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These are herbivores with a tendency to omnivory. They prefer
fruits, but also subsist on tubers, grains, vegetables, leaves, legume
pods, and wastes (such as banana peels). However, they are not grass-
eaters. Giant rats also kill and eat mice, insects (caterpillars, cock-
roaches, and locusts, for example), and probably many other small
animals.3 They are particularly fond of mollusks (such as snails).
Reproduction is prolific and year-round. The female attains puberty
at 2~23 weeks and the gestation period is about 2~42 days. The
young are weaned at 21-26 days of age but stay with their mother until
2-3 months of age. So far, the record for the most litters has been 5
in 9 months. It thus seems possible that a female can reproduce 6
times a year. Litter size ranges between 1 and 5, but 4 is most common.
Thus, in 1 year a single female could produce 24 or more young.
BEHAVIOR
These strictly nocturnal animals usually lead solitary lives and forage
alone. Mostly, they occupy a burrow by themselves, except when the
3 Information from M. Malekani.
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MICROLIVESTOCK
young are being raised. The burrows can be complex. Below the
entrances are vertical shafts leading to a system of galleries and
chambers for storing food, depositing droppings, sleeping, or breeding.
The home range is individual and limited (1 - hectares). In the wild,
one male "supervises" the home ranges of several females.
In captivity, the animals are often seen sitting up and ramming large
amounts of food into their spacious cheek pouches. With full cheeks,
they return to their burrows and disgorge the food into a "larder."
Food (chiefly hard nuts) is stored there.
They swim and climb well.
USES
A study carried out in Nigeria showed that the giant rat produces
about the same amount of meat as the domestic rabbit.4 The meat's
nutritional value compares favorably with that of domestic livestock,
and African villagers know how to preserve it by smoking or by salting.
The giant rat has recently attracted attention as a potential laboratory
animal.
HUSBANDRY
Farmers in Nigeria have traditionally trapped the juveniles and
fattened them for slaughter. They usually keep the animals in wire
cages and feed them daily with food gathered in the wild as well as
with scraps from the household.
As noted, the program at the University of Ibadan indicates that the
giant rat can be domesticated. Already, specimens are being bred and
reared in an intensive program. They adapt to captivity after about a
month. They are subsequently transferred into breeding cages, which
are wooden boxes with a rectangular wire-mesh "playroom." Each
cage holds a breeding pair or a nursing female with its young.
Experimental feeding cages have also been designed.5
Food-preference trials show that palm fruits and root crops (espe-
cially sweet potato) are preferred to grains and vegetables. Nutritional
studies show that the animals can tolerate up to 7 percent crude fiber
in their rations. Although largely vegetarian, they eagerly consume
dry and canned dog food.
4 Ajayi, 1975
5 Information from S.S. Ajayi.
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GIANT RAT
ADVANTAGES
These animals have several advantages:
229
· They are well known and much sought after for food.
· They have adapted to life in lowland tropics.
· They are able to live on locally available plant materials, including
vegetable waste.
· They reproduce rapidly.
· They are more tolerant of captivity than the grasscutter (see next
chapter). This is largely because omnivorous feeding makes them
easier to feed than the grasscutter and other strict herbivores.
LIMITATIONS
This species could easily become a pest. It is recommended for
rearing only in areas where it already exists. The crops it damages
include cacao, root crops, peanuts, maize, sorghum, vegetables, and
stored grains and foods. There is also the possibility that this rodent
may transmit diseases to humans.
A project at the University of Kinshasa in Zaire reports problems
in getting giant rats to reproduce in captivity. When two specimens
were paired they sometimes fought so viciously that copulation was
impossible.6 Special management may be required, such as housing
animals in adjacent cages before actually introducing them to each
other. Moreover, selection for docility may also be necessary.
The ratlike appearance is not attractive, and a few African tribes
have taboos against consuming the meat of these animals.
RESEARCH AND CONSERVATION NEEDS
Throughout Africa south of the Sahara, giant rat domestication
deserves experimentation and trials. Success would open up the
potential for supplemental meat supplies in rural and urban areas
where meat is now scarce. Tests are needed to determine the factors
that favor breeding: temperature, aeration, light, privacy, and size and
form of cages. Moreover, diets that are cheap and easy to make from
local feedstuffs must be identified.
6 Information from M. Malekani, who adds that "the rainforest species seems more
docile and sociable than the C. gambianus in our domestication."
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MICROLIVESTOCK
Further research on the domestication of the giant rat might include:
· Identifying husbandry techniques that are applicable at low cost
in rural areas;
· Studying food digestibility and setting up various diets;
· Illuminating social behavior: pairing of animals, the best moment
for pairing, duration of pairing, age of partners;
· Outlining the basics of husbandry (for instance, capital costs, food
conversion ratios, growth rates) and making simple and cheap cages;
· Studying biology (anatomy, physiology, birth records, growth
rated; and
· Testing the practical likelihood that this rodent may transmit
diseases to people and other animals.
The giant rat has an interesting commensal relationship with Hem-
imerus, an insect that feeds on secretions in the skin. It seems to cause
no irritation or damage, and may even benefit the host by helping to
keep the skin clean. Caging these animals results in the general loss
of the insect, but attempts should be made to maintain them and to
determine their role and life cycle.7
The potential of this species as a laboratory animal in nutritional,
clinical, and pharmacological research also deserves exploration.
7 Information from M. Malekani.
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Representative terms from entire chapter:
giant rats
