Ctenomys rionegrensisRio Negro tuco-tuco

Ge­o­graphic Range

Rio Negro tuco-tu­cos are found in four pop­u­la­tions: one oc­cu­pies a small re­gion of west­ern Uruguay in the De­part­ment of Rio Negro, and the re­main­ing three are found in the Entre Rios Province in east­ern Ar­gentina. (Bidau, et al., 2008; Wla­siuk, et al., 2003)

Habi­tat

Rio Negro tuco-tu­cos gen­er­ally in­habit sand dunes and areas with sandy soils near the mouth of the Rio Uruguay, along the Rio Parana, and near the Rio Negro. (Bidau, et al., 2008; D'Ana­tro and Lessa, 2006)

  • Range elevation
    0 to 200 m
    0.00 to 656.17 ft

Phys­i­cal De­scrip­tion

Rio Negro tuco-tu­cos are ro­dents with short necks, large heads with re­duced ears, and short fore­limbs with large claws. They are well suited for a fos­so­r­ial lifestyle. Adults gen­er­ally weigh be­tween 100 and 700 grams and grow to 15 to 25 cen­time­ters from snout to tail. The tail is hair­less and stiff. Three dis­tinct fur col­ors are found among these tuco-tu­cos: melanic (black), agouti (light and dark banded hairs with black tips), and dark-backed. How this vari­a­tion arose ge­net­i­cally is being in­ves­ti­gated. The ro­bust in­cisors are or­ange on the an­te­rior sur­face and are ever-grow­ing. Rio Negro tuco-tu­cos can be dis­tin­guished from other tuco-tu­cos by the male phal­lus which has a “trilobed bac­u­lar tip and a pair of spikes within the in­tro­mit­tent sac.” Rest­ing meta­bolic rates have not been cal­cu­lated, but the basal meta­bolic rate of a sim­i­lar species (Cteno­mys aus­tralis) is around 0.343±0.053 liters of oxy­gen per hour. (Al­tuna and Lessa, 1985; Lacey, et al., 2000; Wla­siuk, et al., 2003)

  • Range mass
    100 to 700 g
    3.52 to 24.67 oz
  • Range length
    15 to 25 cm
    5.91 to 9.84 in

Re­pro­duc­tion

Lit­tle is known about the mat­ing sys­tem of Rio Negro tuco-tu­cos. Pre­sum­ably, it is sim­i­lar to Pear­son's tuco-tu­cos, Cteno­mys pear­soni, which have been bet­ter stud­ied. Courtship rit­u­als in­volve ag­gres­sive dis­plays be­tween males and chem­i­cal and au­di­tory stim­u­la­tion. Rio Negro tuco-tu­cos sing dur­ing courtship. Males spend time with fe­males be­fore cop­u­lat­ing, as fe­males are in­duced ovu­la­tors. ("Gabriel Francescoli", 2005; Al­tuna, et al., 1991; Francescoli, 1999; Lacey, et al., 2000)

The breed­ing sea­son of Rio Negro tuco-tu­cos oc­curs dur­ing the late aus­tral au­tumn. In a study by Tassino and Pas­sos (2009), preg­nant fe­males were ob­served dur­ing the be­gin­ning of aus­tral win­ter and lac­tat­ing fe­males were ob­served dur­ing the aus­tral spring. Fe­males gen­er­ally bear 2 to 4 off­spring after ges­tat­ing for 100 days and lac­tate for about two months. Av­er­age time to wean­ing and av­er­age birth mass is un­known. In Cteno­mys ta­larum av­er­age time to wean­ing is around 30 days from birth and the birth mass is 46.0 ± 16.43g. ("Tuco-Tu­cos: Cteno­myi­dae - Be­hav­ior And Re­pro­duc­tion", 2010; Tassino and Pas­sos, 2010; Zenuto, et al., 2002)

  • Breeding interval
    Rio Negro tuco-tucos breed once yearly.
  • Breeding season
    Rio Negro tuco-tucos breed during the austral autumn (March to June).
  • Range number of offspring
    2 to 4
  • Average gestation period
    100 days

After cop­u­la­tion, males and fe­males sep­a­rate, with fe­males tak­ing care of the young until they be­come in­de­pen­dent.

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

Lifes­pan/Longevity

Lit­tle is known about the lifes­pan of Rio Negro tuco-tu­cos in cap­tiv­ity, but the ex­pected lifes­pan in the wild is about 3 years.

  • Average lifespan
    Status: wild
    3 years

Be­hav­ior

Rio Negro tuco-tu­cos are soli­tary and ter­ri­to­r­ial, so­cial­iz­ing only to mate. They are semi-fos­so­r­ial, re­sid­ing in bur­rows which they dig with their in­cisors. (Francescoli, 1999; Lacey, et al., 2000; "Tuco-Tu­cos: Cteno­myi­dae - Be­hav­ior And Re­pro­duc­tion", 2010)

Home Range

Lit­tle is known re­gard­ing the home range of Rio Negro tuco-tu­cos. Be­cause these are fos­so­r­ial an­i­mals, they pre­sum­ably do not ven­ture far from their bur­rows.

Com­mu­ni­ca­tion and Per­cep­tion

Rio Negro tuco-tu­cos sig­nal to each other over long dis­tances by "singing." The name "tuco-tuco" comes from the sound these an­i­mals make. A record­ing of their vo­cal­iza­tions can be found here: http://​eto.​fcien.​edu.​uy/​gaboeng.​htm. These an­i­mals com­mu­ni­cate to de­mar­cate ter­ri­tory and to find each other dur­ing the mat­ing sea­son. ("Gabriel Francescoli", 2005; Francescoli, 1999)

Food Habits

Rio Negro tuco-tu­cos are her­biv­o­rous, pri­mar­ily eat­ing grasses, roots, and shoots. Like rab­bits, they are co­prophagous. ("Tuco-Tu­cos: Cteno­myi­dae - Be­hav­ior And Re­pro­duc­tion", 2010)

  • Plant Foods
  • leaves
  • roots and tubers
  • Other Foods
  • dung

Pre­da­tion

The dull coat color of Rio Negro tuco-tu­cos is an ex­am­ple of cryp­tic col­oration, as it would make them dif­fi­cult to spot on a river­bank. Some preda­tors in­clude owls, foxes, ar­madil­los, gri­son, and some snakes. (Wla­siuk, et al., 2003)

  • Anti-predator Adaptations
  • cryptic

Ecosys­tem Roles

Lit­tle is known about the sub­tleties of the eco­log­i­cal role of Rio Negro tuco-tu­cos. Birds of prey, large snakes, and sev­eral car­niv­o­rous mam­mals prey on this ro­dent, and pre­sum­ably some par­a­sites would use them as hosts, al­though this is not well-stud­ied. Rio Negro tuco-tu­cos are shy and soli­tary and are not com­men­sals with hu­mans. (Lacey, et al., 2000; Lacey, et al., 2000)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Rio Negro tuco-tu­cos are not known to ben­e­fit hu­mans, but be­cause three fur phe­no­types exist within rel­a­tively small iso­lated pop­u­la­tions and be­cause of pro­found dif­fer­en­ti­a­tion within the species, they are cur­rently being in­tensely stud­ied by evo­lu­tion­ary bi­ol­o­gists.

  • Positive Impacts
  • research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of Rio Negro tuco-tu­cos on hu­mans.

Con­ser­va­tion Sta­tus

Rio Negro tuco-tu­cos are listed as an en­dan­gered species on the IUCN Red List be­cause "its ex­tent of oc­cur­rence is less than 5,000 km², its area of oc­cu­pancy is less than 500 km², its dis­tri­b­u­tion is se­verely frag­mented, there are only four pop­u­la­tions and there is con­tin­u­ing de­cline in the ex­tent and qual­ity of its habi­tat. It may be lo­cally abun­dant if habi­tat is avail­able but habi­tat is being quickly de­stroyed." (Bidau, et al., 2008)

Con­trib­u­tors

Cris­t­ian Cha­gas (au­thor), Michi­gan State Uni­ver­sity, Bar­bara Lun­dri­gan (ed­i­tor), Michi­gan State Uni­ver­sity, Tanya Dewey (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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

cryptic

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.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
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.

female parental care

parental care is carried out by females

folivore

an animal that mainly eats leaves.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

herbivore

An animal that eats mainly plants or parts of plants.

induced ovulation

ovulation is stimulated by the act of copulation (does not occur spontaneously)

iteroparous

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).

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.

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

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

tropical

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

tropical savanna and grassland

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.

savanna

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.

temperate grassland

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.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

Ref­er­ences

2010. "Ar­gentina Land Sales" (On-line). Ac­cessed March 15, 2010 at http://​www.​argentinalandsales.​com/​pentrerios.​htm.

2005. "Gabriel Francescoli" (On-line). Ac­cessed March 10, 2010 at http://​eto.​fcien.​edu.​uy/​gaboeng.​htm.

Net In­dus­tries. 2010. "Tuco-Tu­cos: Cteno­myi­dae - Be­hav­ior And Re­pro­duc­tion" (On-line). Ac­cessed March 11, 2010 at http://​animals.​jrank.​org/​pages/​3473/​Tuco-Tucos-Ctenomyidae-BEHAVIOR-REPRODUCTION.​html.

Al­tuna, C., G. Francescoli, G. Izquierdo. 1991. Cop­u­la­tory Pat­tern of Cteno­mys pear­soni (Ro­den­tia, Octodon­ti­dae) from Bal­n­eario Solís, Uruguay. Mam­malia, 55: 214.

Al­tuna, C., E. Lessa. 1985. Pe­nial Mor­phol­ogy in Uruguayan Species of Cteno­mys (Ro­den­tia; Octodon­ti­dae). Jour­nal of Mam­mal­ogy, 66:3: 483-488.

Bidau, C., E. Lessa, R. Ojeda. 2008. "Cteno­mys ri­one­gren­sis. In: IUCN 2010. IUCN Red List of Threat­ened Species. Ver­sion 2010.1" (On-line). Ac­cessed March 15, 2010 at www.​iucnredlist.​org.

D'Ana­tro, A., E. Lessa. 2006. Geo­met­ric mor­pho­me­t­ric analy­sis of ge­o­graphic vari­a­tion in the Río Negro tuco-tuco, Cteno­mys ri­one­gren­sis (Ro­den­tia: Cteno­myi­dae). Mam­malian Bi­ol­ogy, 71:5: 288-298.

Francescoli, G. 1999. A Pre­lim­i­nary Re­port on the Acoustic Com­mu­ni­ca­tion in Uruguayan Cteno­mys (Ro­den­tia, Octodon­ti­dae): Basic Song Types. Bioa­coustics, 10: 203.

Francescoli, G., C. Al­tuna. 1998. Vi­bra­tional Com­mu­ni­ca­tion in Sub­ter­ranean Ro­dents: The Pos­si­ble Ori­gin of Dif­fer­ent Strate­gies. Evo­lu­tion of Com­mu­ni­ca­tion, 2: 217.

Lacey, E., J. Pat­ton, G. Cameron. 2000. Life Un­der­ground. Chicago: Chicago Uni­ver­sity Press.

Luna, F., C. An­tenucci, F. Bozi­novic. 2009. Com­par­a­tive En­er­get­ics of the Sub­ter­ranean Cteno­mys Ro­dents: Break­ing Pat­terns. Phys­i­o­log­i­cal and Bio­chem­i­cal Zo­ol­ogy, 82/3: 226-235.

Tassino, B., C. Pas­sos. 2010. Re­pro­duc­tive Bi­ol­ogy of Rio Negro tuco-tuco, Cteno­mys ri­one­gren­sis (Ro­den­tia: Octodon­ti­dae). Mam­malian Bi­ol­ogy, 75:13: 253-260.

Wla­siuk, G., J. Garza, E. Lessa. 2003. Ge­netic And Ge­o­graphic Dif­fer­en­ti­a­tion In The Rio Negro Tuco-Tuco (Cteno­mys ri­one­gren­sis): In­fer­ring The Roles Of Mi­gra­tion And Drift From Mul­ti­ple Ge­netic Mark­ers. Evo­lu­tion, 57:4: 913-926.

Zenuto, R., C. An­ti­nuchi, C. Busch. 2002. Bioen­er­get­ics of Re­pro­duc­tion and Pup De­vel­op­ment in a Sub­ter­ranean Ro­dent. Phys­i­o­log­i­cal and Bio­chem­i­cal Zo­ol­ogy, 75: 469-478.