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Thryonomys swinderianusgreater cane rat

By Emily Gochis

Geographic Range

Thryonomys swinderianus is common in Africa, south of the Sahara. It ranges from Gambia to southern Sudan and from south to north Namibia and South Africa. Its range does not include the southwest portion of South Africa (Fritzinger, 1997).

Habitat

T. swinderianus is found naturally near marshes and river banks (Mills, 1997). Populations can also reach very high densities in plantations of cultivated crops (Merwe, 2000). Its habitat is expanding due to farmers turning once undesirable forest land into farmland (Asibey,1999).

Physical Description

The body length of T. swinderianus is usually 350-610 mm, and their tail reaches 65- 260 mm in length (Fitzinger,1997). Great Cane Rats’ heavyset bodies have an average weight in males of 4.5 kg and 3.5 kg in females (Merwe, 2000). They have a rounded nose, short ears, and incisors that grow continuously (Mills, 1997). The pelage is coarse, with flattened bristle like hairs that grow in groups of five or six. The upper parts are a yellowish brown color and the underside is a much lighter gray. Great Cane Rats have no under fur (Fitzinger, 1997). The forefeet are smaller than the hind feet and have three well developed middle digits with the first and fifth digits greatly reduced. The hind feet have no first digit and all digits have heavy claws (Fitzinger, 1997). The dental formula for T. swinderianus is 1/1, 0/0, 1/1, 3/3 (Maerwe, 2000).

  • Range mass
    3 to 9 kg
    6.61 to 19.82 lb
  • Average mass
    3.5-4.5 kg
    lb
  • Range length
    350 to 610 mm
    13.78 to 24.02 in

Reproduction

T. swinderianus live in groups of males and females during the breeding season. When the dry season comes males separate from the group and live by themselves. The females continue to live together (Fitzinger, 1997).

The breeding time depends on which part of Africa the animal is found and seems to depend on the weather (Fitzinger, 1997). The wet season of the year is the usual breeding season. Females generally have two litters per year with usually 4 offspring (Mills, 1997). Great Cane Rats estrous cycle usually lasts 6.62 days and they have a gestation period of 137- 172 days (Fitzinger, 1997). Offspring weigh about 129 grams and are relatively well developed. Their eyes are open, they are covered in hair and can run. T. swinderianus become sexually mature at about a year old (Fitzinger, 1997).

  • Range number of offspring
    1 to 6
  • Average number of offspring
    4
  • Average number of offspring
    4
    AnAge
  • Range gestation period
    137 to 172 days
  • Average gestation period
    155 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days
    AnAge

Lifespan/Longevity

Fritzinger (1997) desribed a T. swinderianus that lived in captivity for four years and four months.

Behavior

T. swinderianus can be usually found in groups composed of one male, several females, and young from more than one generation (National Research Council, 1991). They are nocturnal and create trails through grass and reeds that lead from shelter to feeding and water sites. They pound down tall grass to make nests and also make shallow burrows for shelter. They are good swimmers and divers (Fitzinger, 1997). If Great Cane Rats become afraid they either stomp their hind feet and grunt or quickly run towards water (National Research Council, 1991). Fitzinger (1997) describes males fighting by having a nose to nose pushing duel. He did not observe males fighting with females or young.

Communication and Perception

Food Habits

T. swinderianus are herbivores and their natural diet is mainly grasses and cane. Sometimes they also eat bark, fallen fruits, nuts and many different kinds of cultivated crops. Some of the cultivated crop fields that T. swinderianus invade are sugar cane, maize, millet, cassava, roundnuts, sweet potatoes, and pumpkins (Fitzinger, 1997). Great Cane Rats’ favorite food is elephant grass and sweet potatoes (National Research Council, 1991). They prefer plants with lots of moisture and soluble carbohydrates (Agbelusi, 1997).

T. swinderianus cut the grasses and other foods with their incisors, producing a chattering sound that is relatively loud and very distinguishable (Mills, 1997).

  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit

Economic Importance for Humans: Positive

T. swinderianus is one of the most preferred meats in Africa and it can be more expensive than lamb, chicken, beef, or pork (National Research Council, 1991). It has been sold in Ghana markets for almost twice as much as beef and pork. In one African market, about 200,000 kg, which is worth about $220,000 U.S., was sold in a year’s time (Fitzinger, 1997). Asibey (1999) believes that if more research was done to find the most efficient way to breed T. swinderianus, then these animals would be the solution to Africa's protein shortage.

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

T. swinderianus are considered to be great pests of many cultivated crops and can do great economical harm to farmers (Merwe, 2000).

  • Negative Impacts
  • crop pest

Conservation Status

T. swinderianus population is not threatened by extinction, although individual populations may be extinct locally due primarily to over hunting (National Research Council, 1991).

Contributors

Emily Gochis (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

young precocial

young are relatively well-developed when born

References

Agbeluski, E. 11/13/97. "RANCHING GRASSCUTTER THRYONOMYS SWINDERIANUS T. FOR MEAT PRODUCTION IN THE HUMID FOREST ZONE OF NIGERIA" (On-line). Accessed 11/19/01 at http://www.fao.org/montes/foda/wforcong/PUBLI/V3/T18E/2-2.HTML.

Asibey, E., P. Addo. 1999. "THE GRASSCUTTER (Thryonomys swinderianus) -" (On-line). Accessed 11/12/01 at http://www.cdr.dk/sscafrica/as&ad-gh.htm.

Fitzinger, 1995. Cane Rats. Pp. 1650-1651 in R Nowak, ed. Walker's Mammals of the World. The Johns Hopkins University Press.

Merwe, M. August 2000. Tooth succession in the greater can rat Thryonomys swinderianus. Journal of Zoology, 251: 541-545.

Mills, G., L. Hes. 1997. The complete book of South African Mammmal. Capetown: Struik Winchester.

National Reasearch Counsil, 1991. Microlivestock: Little-Known Small Animals with a Promising Economic Future. Washington DC: National Academic Press.

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