Animal Diversity Web

Ge­o­graphic Range

The genus Thry­on­o­mys is re­stricted to sub-Sa­ha­ran Africa. Thry­on­o­mys gre­go­ri­anus 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)

• Biogeographic Regions
• ethiopian
  • native

Habi­tat

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)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• savanna or grassland

• Range elevation

  2,600 (high) m

  ft

Phys­i­cal De­scrip­tion

Thry­on­o­mys gre­go­ri­anus is the smaller of the two ex­tant species in the genus 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)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Range mass

  2.65 to 7.50 kg

  5.84 to 16.52 lb

• Average length

  380 mm

  14.96 in

Re­pro­duc­tion

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)

• Mating System
• polygynous

Al­though lit­tle is known about re­pro­duc­tion in T. gre­go­ri­anus, 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 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)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

• Breeding interval

  Two litters a year are possible under favorable conditions.

• Breeding season

  Breeding usually occurs during the wetter months.

• Average number of offspring

  2-3

• Average gestation period

  3 months

• Average age at sexual or reproductive maturity (female)

  1 years

• Average age at sexual or reproductive maturity (male)

  1 years

Thry­on­o­mys gre­go­ri­anus young are born pre­co­cial, are ac­tive shortly after birth, de­velop rapidly, and are suck­led by the fe­male in grass nests (forms). (King­don, 1984)

• Parental Investment
• precocial
• female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifes­pan/Longevity

It is thought that Thry­on­o­mys gre­go­ri­anus in­di­vid­u­als rarely live past three years. (King­don, 1984)

• Range lifespan
  Status: wild

  3 (high) years

Be­hav­ior

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)

• Key Behaviors
• terricolous
• nocturnal
• motile
• sedentary
• solitary
• territorial

• Range territory size

  3,000 to 4,000 m^2

Home Range

Thry­on­o­mys gre­go­ri­anus fam­ily groups have ter­ri­tory sizes of 3,000 to 4,000 square me­ters. (Nowak, 1991)

Com­mu­ni­ca­tion and Per­cep­tion

Thry­on­o­mys gre­go­ri­anus in­di­vid­u­als have poor eye­sight, but good senses of smell and hear­ing. Vo­cal­iza­tions in­clude whistling and low hoot­ing grunts. They will also thump their hind feet when alarmed. (King­don, 1984; Nowak, 1991)

• Communication Channels
• tactile
• acoustic
• chemical

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

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. Thry­on­o­mys gre­go­ri­anus in­di­vid­u­als also prac­tice co­prophagy. (King­don, 1984; Nowak, 1991; Opara, 2010)

• Primary Diet
• herbivore
  • folivore
  • lignivore

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

• Other Foods
• dung

Pre­da­tion

Preda­tors in­clude hu­mans, ser­vals, leop­ards, viver­rids, pythons, and var­i­ous birds of prey. (Dro­nen, et al., 1999; King­don, 1984)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • humans (Homo sapiens)
  • servals (Leptailurus serval)
  • leopards (Panthera pardus)
  • genets, civets, and relatives (Viverridae)
  • pythons (Pythonidae)
  • birds of prey (Falconiformes)

Ecosys­tem Roles

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)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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)

• Positive Impacts
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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)

• Negative Impacts
• crop pest

Con­ser­va­tion Sta­tus

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)

• IUCN Red List

  Least Concern

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Brian Kiss (au­thor), Uni­ver­sity of Man­i­toba, Jane Wa­ter­man (ed­i­tor), Uni­ver­sity of Man­i­toba, Tanya Dewey (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

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.