The genus Thryonomys is restricted to sub-Saharan Africa. occurs throughout eastern Africa and into western Africa in the countries of Cameroon, the Central African Republic, Chad, the Democratic Republic of Congo, Kenya, Malawi, Sudan, Tanzania, Uganda, and Zambia. An isolated population also exists in Zimbabwe and Mozambique. It is likely that populations exist in Angola, however no records have been collected west of the Zambian border. (Antonanzas, et al., 2004; Skinner and Chimimba, 2005)
Lesser cane rats, occasionally referred to as savanna cane rats, inhabit moist grasslands dominated by elephant grass (Pennistum purpureum). They are also occasionally found along the fringes of swamps and in wooded areas. Individuals usually use tall grass for shelter, but have also been found digging shallow burrows or using rock crevices, termite mounds, and abandoned aardvark or porcupine holes. This species is considered non-aquatic, differing in habitat preference from the semi-aquatic Thryonomys swiderianus. Individuals have been recorded up to altitudes of 2,600 m. (Ansell, 1966; Kingdon, 1984; Nowak, 1991; Sheppe and Osborne, 1971)
Thryonomys. Thryonomys swinderianus is the larger of the two species. Lesser cane rat body measurements are: average head to tail length 380 mm; average tail length 90 mm; and average hind foot length 59 mm. Body mass can range from 2.65 to 7.5 kg. Thryonomys species are covered with bristle-like hairs that grow in groups of five or six, and lay longitudinally along their bodies. They lack underfur. Typical body coloration is speckled grayish brown or yellowish brown on the back and flanks, with grey or whitish under parts. The tail is sparsely covered with short bristle-like hairs, with scales present between hairs. The tail is brownish above and whitish underneath. Ears are short, rounded, and hardly extend beyond the body pelage. The forefoot has three well-developed central digits, while the first and fifth digits are smaller and almost non-functional. On the hind foot the digits are larger, but the first digit is absent. Each foot possesses a naked palm and thick, heavy claws. Lesser cane rats have short tails that barely extend past their outstretched hind foot. This is a distinguishing characteristic from their close relative, T. swinderianus, which has a tail twice the length of the foot. Lesser cane rats have two paired mammae compared with three in T. swinderianus. The dental formula is: i 1/1, c 0/0, pm 1/1, m 3/3. Adult skulls can be identified by the placement of three groves on the anterior surface of each upper incisor. The third, outermost groove is located near the outside edge of the tooth, rather than along the midline of the tooth as in T. swinderianus. Most adult and juvenile skulls can also be differentiated from T. swinderianus skulls by the presence of a bar across each foramen ovale, a square appearance of the pair frontal bones when viewed dorsally, and a right angle orientation of the zygomatic arch and the dorsal and ventral attachments of the outer rim of the infraorbital foramen on the lateral side of the skull. (Kingdon, 1984; Nowak, 1991; Thomas, 1922; Van der Merwe, 2007)is the smaller of the two extant species in the genus
In Thryonomys species, males initiate courtship by wagging their tails and treading the hind legs. If the female is attracted to these actions, the pair will rear up and touch noses, followed by copulation. Male cane rats also use nose to nose pushing duels to establish a dominance hierarchy within in their social group, which presumably influences mate selection by females. (Ewer, 1968; Kingdon, 1984)
Although little is known about reproduction in Thryonomys species reach sexual maturity after one year. Scarce records show pregnant females carrying 2 to 3 fetuses. Gestation in Thryonomys lasts approximately three months. Due to this low reproductive potential, exploited populations may take long periods of time to recover. (Fiedler, 1994; Kingdon, 1984; Skinner and Chimimba, 2005), in most regions they seem to be seasonal breeders, reproducing during the wetter months. Two litters a year are possible under favorable conditions. It is thought that
It is thought that (Kingdon, 1984)individuals rarely live past three years.
Lesser cane rats are solitary in their habits, but can occupy a restricted area with a small family of up to a dozen individuals. They are primarily nocturnal, but are occasionally active during the day. Dominance fighting between males involves a nose to nose pushing duel. Both individuals push until one relieves pressure, causing the dominant individual to whip its rump around and hit its opponent, knocking the weaker individual off balance. (Ewer, 1968; Nowak, 1991; Skinner and Chimimba, 2005)
Lesser cane rats are herbivores that feed mainly on grasses and cane, but also feed on nuts, bark, fruits, and cultivated crops. They commonly gnaw on rocks, bones, and ivory. Lesser cane rat habitat is typically dominated by elephant grass and is therefore considered a principal food source. It is common for groundnut, sweet potato, cassava, maize, and pumpkin crops to be preyed on by these cane rats. (Kingdon, 1984; Nowak, 1991; Opara, 2010)individuals also practice coprophagy.
Lesser cane rats provide nutrition as a prey species to their predators. A species of anoplocephalid tapeworm, Thysanotaenia congolensis, was discovered in lesser cane rats in the Lake Kivv area of the Democratic Republic of Congo. They are the only known host for this species of tapeworm. (Dronen, et al., 1999; Kingdon, 1984)
Thryonomys species are intensively hunted as an important source of protein throughout their range. They are typically hunted with dogs, spears, and fall-traps, or by burning vegetation. It is estimated that, in West Africa, 80 million are harvested annually, equaling 300,000 metric tons of meat. To increase meat availability, Thryonomys species have been domesticated and currently efforts are being made to expand the industry. Greater cane rats are preferred over lesser cane rats because of their larger body size, however it has been suggested that both species should be reared as part of the industry. Thryonomys species meat has more protein than chicken, rabbit, and guinea pig and lower fat than pork, beef, and lamb. The expansion of this domesticated market may also relieve pressure on wild populations of cane rats. (Fiedler, 1994; Hoffmann, 2008a; Howell, 1981; Jori, et al., 1995)
Thryonomys species can do considerable damage to sugar cane fields. Many plantations protect predators, such as pythons so that they can prey on cane rats, lessening crop damage. Cane rats also damage maize, millet, groundnut, sweet potato, cassava, and pumpkin fields. (Nowak, 1991)
The ICUN Red List of Threatened Species lists lesser cane rats as a species of least concern due to their large population and wide distribution. (Hoffmann, 2008b)
Brian Kiss (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
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.
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
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.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
having more than one female as a mate at one time
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
Ansell, W. 1966. Thryonomys gregorianus and Thryonomys swinderianus in Zambia. The Puku, 4: 1-16.
Antonanzas, R., S. Sen, P. Mein. 2004. Systematics and phylogeny of the cane rats (Rodentia: Thryonomyidae). Zoological Journal of the Linnean Society, 142: 423-444.
Dronen, N., S. Simeik, J. Scharninghausen, R. Pitts. 1999. Thysanotaenia congolensis n. sp. (Cestoda: Anoplocephalidae) in Lesser Savanna Cane Rat, Thryonomys gregorianus from Democratic Republic of Congo, Africa. The Journal of Parasitology, 85: 90-92.
Ewer, R. 1968. Form and function on the grass cutter, Thryonomys swinderianus Temm. (Rodentia: Thryonomyidae)). Ghana Journal of Science, 9: 131-141.
Fiedler, L. 1994. Rodent pest management in eastern Africa. Rome: Food and Agriculture Organization of the United Nations.
Hoffmann, L. 2008. The yield and nutritional value of meat from African ungulates, camelidae, rodents, ratites, and reptiles. Meat Science, 80: 94-100.
Hoffmann, M. 2008. "Thryonomys gregorianus" (On-line). ICUN Red List of Threatened Species. Version 2011.2. Accessed November 29, 2011 at www.icunredlist.org.
Howell, K. 1981. A note on the identification of cane rats, with records from Dar es Salaam. Bulletin - East Africa Natural History Society, 1981: 41-43.
Jori, F., G. Mensah, E. Adjanohoun. 1995. Grasscutter production: and example of rational exploitation of wildlife. Biodiversity and Conservation, 4: 257-265.
Kingdon, J. 1984. Thryonomyid Rodents. Pp. 696-704 in East African Mammals, Vol. 2, Part B (hares and rodents). Chicago, Illinois: University of Chicago Press.
Nowak, R. 1991. Cane Rats. Pp. 956-957 in Walker's mammals of the world, Vol. 2, 5th Edition. Baltimore: The John Hopkins University Press.
Opara, M. 2010. Grasscutter: the haematology and major parasites. Research Journal of Parasitology, 5: 214-223.
Sheppe, W., T. Osborne. 1971. Patterns of use of a flood plain by Zambian mammals. Ecological Monographs, 41: 179-205.
Skinner, J., C. Chimimba. 2005. Lesser canerat. Pp. 96-97 in The mammals of the South African subregion, 3rd Edition. Cambridge: Cambridge University Press.
Thomas, O. 1922. On the animals known as ground-hogs or cane-rats in Africa. Annals & Magazine of Natural History, 9: 388-392.
Van der Merwe, M. 2007. Discriminating between Thryonomys swinderianus and Thryonomys gregorianus. African Zoology, 42: 165-171.