(Ctenomyidae)
Class: Mammalia
Order: Rodentia
Suborder: Hystricognathi
Family: Ctenomyidae
Thumbnail description
Small- to medium-sized herbivores, big head, strong and big incisors, reduced ears, heavily built body, medium tail, powerful nails with supraungual comb-like hairs
Size
Body length 8.6–16.9 in (22–43 cm); weight 3.5–38.8 oz (100–1,100 g)
Number of genera, species
1 genus; 58 species
Habitat
Subterranean
Conservation status
Vulnerable: 1 species; Lower Risk/Near Threatened: 3 species
Distribution
South America, in southern Peru, Bolivia, Chile, Paraguay, Argentina, Uruguay, and southern Brazil
Evolution and systematics
Today, Ctenomyidae has one living genus with 58 species and eight fossil genera. These numbers are highly variable, because description of new species and reconsideration of old ones continues. Genus Ctenomys exists from the lower Pleistocene, and Ctenomyidae is found from the upper Miocene. Among the Hystricognathi, Ctenomyidae is closely related to: Octodontidae (octodonts), Abrocomidae (chinchilla rat), and Myocastoridae (coypu). Ctenomys is the most specious group of living rodents.
Physical characteristics
The head is big and there is no evident neck. Incisors are big, strong, easily visible, and generally have an orange coloration on their frontal side. Limbs are powerful and short, and the ears are reduced. Their forepaws sport strong nails with characteristic supraungual hair combs. The tail is medium in length, stiff, and almost hairless.
Size ranges approximately from 8.6 in (22 cm) in C. pundti to 16.9 in (43 cm) in C. conoveri (total length), and their weights vary 3.5–38.8 oz (100–1,100 g).
The coat color is also variable, from pale to black. The majority of the species have brown reddish pelage.
Distribution
Ctenomys lives exclusively in South America, from 12° to 54°S latitude and from Pacific to Atlantic coasts. Current range includes southern Peru, Bolivia, Chile, Paraguay, Argentina, Uruguay, and southern Brazil.
Habitat
Tuco-tucos live in many habitats: grasslands, semi-arid lands, coastal dunes, forest meadows, and steppes, and from the sea level up to 13,120 ft (4,000 m) in the Andes. They perform almost all their activities underground, except for some foraging and, eventually, young dispersal.
Tuco-tucos dig tunnel systems that are exclusive for each individual (solitary) or for multiple animals (social). Their burrows are at depths varying 11.8–118 in (30–300 cm), built as central tunnels with branching secondary tunnels, and have multiple holes communicating with the surface usually closed with soil plugs that can be open or closed at will. The tunnel system then acts not only as an anti-predator defensive device, but also allows the animal to maintain a humidity level always near 100% and an almost stable temperature level through the year.
Behavior
Tuco-tucos are mostly solitary animals. Individuals get together only during the mating season for copulation and, after pregnancy, the pups remain with the mother for a few months before dispersing. Some species have been suggested as social, but that condition is confirmed only for Ctenomys sociabilis.
Ctenomys uses sounds, odors, and touch to communicate with each other. Tactile communication appears at close contact. Urine and feces act as chemical signals. General knowledge about them is scarce.
Vocalizations have been reported for many Ctenomys species, both solitary and social. Solitary animals have limited repertoires of four to six different signals. The common name of these animals (tuco-tuco) is an onomatopoeic representation of their territorial/warning vocalizations that can be heard from fairly great distances outside their burrows. Most common vocal signals for solitary animals are territorial, aggressive, male courting (guttural sounds), female-mounting acceptance, and pup contact/isolation calls (with a "crying" quality).
The majority of the solitary species of Ctenomys are territorial and they maintain separate burrows, using warning signals. In social animals, each colony maintains their burrow system independent from others, also using signals. Solitary animals are very aggressive. Social animals also have aggressive behaviors, but they can be more tolerant.
Tuco-tucos are thought to be polyrhythmic in their activity patterns, alternating many activity periods with resting or immobility throughout the day. They seem to be basically diurnal, at least for foraging outside their burrows. Nevertheless, the current information available is very scarce. No migratory patterns are known.
Feeding ecology and diet
Tuco-tucos are strictly herbivorous and exhibit a generalist feeding strategy. They feed both on aerial and subterranean (root) parts of grasses, herbs, and shrubs.
They do not drink water; all the water they need is obtained from the plants they eat. They perform fecal reingestion (second passage of fecal pellets through the digestive tract) and have special kidney adaptations. Reingestion and kidney adaptations might be related to water economy and to the recovering of some particular nutrients.
Some species feed aboveground, while other species harvest the food outside and gather it into their burrows to feed.
Reproductive biology
Courtship, mating, and pup lactation occur inside the burrows.
Courtship begins with aggressive postures and continues with an intense exchange of chemical, tactile, and acoustic signals. Long pre-copulatory interaction periods and, in general, more than one copulation occur before ejaculation because of their induced ovulator condition. In induced ovulators, strong stimulation of the female during copulation is needed. The mating system is polygynous.
Gestation takes about 100 days. Two to six pups per litter are born fully developed, and the lactation period duration is about two months. In general, males do not participate in pup care.
One or two reproductive periods per year may appear. In species with only one reproductive period, it occurs during the austral winter.
Conservation status
Some tuco-tucos are common (Ctenomys talarum and C. mendocinus), others are restricted to typical localities. The IUCN lists C. magellanicus as Vulnerable, and C. latro, C. mattereri, and C. sociabilis as Lower Risk/Near Threatened. No other species are listed.
The decline of some populations is mostly due to urbanization, floodings (natural or artificial), or vulcanism.
Population estimates are variable, from one individual per acre (2.5 individuals per ha) (C. opimus) to 84 individuals per acre (207 individuals per ha) (C. talarum).
No conservation efforts are currently known.
Significance to humans
Tuco-tucos appear in many South American indigenous myths and legends (i.e., Tehuelches and Tobas indigenas). Tehuelches and Onas people eat them. Ctenomys is considered a pest in Argentina. Tuco-tucos may cause problems to humans because they consume crops and roots of timber trees. They can also affect human building activities because of their removal of soil.
Species accounts
Pearson's tuco-tucoRio Negro tuco-tuco
Social tuco-tuco
Resources
Books:Lacey, Eileen A., James L. Patton, and Guy N. Cameron, eds. Life Underground. Chicago: University of Chicago Press, 2000.
Reig, Osvaldo A., Cristina Busch, Marcelo O. Ortells, and Julio R. Contreras. "An Overview of Evolution, Systematics, Population Biology, Cytogenetics, Molecular Biology and Speciation in Ctenomys." In Evolution of Subterranean Mammals at the Organismal and Molecular Levels, edited by Eviatar Nevo and Osvaldo A. Reig. New York: Wiley, 1990.
Periodicals:Altuna, Carlos A., Gabriel Francescoli, and Graciela Izquierdo. "Copulatory Pattern of Ctenomys pearsoni (Rodentia, Octodontidae) from Balneario Solís, Uruguay." Mammalia 55 (1991): 214.
Altuna, Carlos A., Gabriel Francescoli, Bettina Tassino, and Graciela Izquierdo. "Ecoetología y Conservación de Mamíferos Subterráneos de Distribución Restringida: El Caso de Ctenomys pearsoni (Rodentia, Octodontidae) en el Uruguay." Etología 7 (1999): 47.
Francescoli, Gabriel. "A Preliminary Report on the Acoustic Communication in Uruguayan Ctenomys (Rodentia, Octodontidae): Basic Song Types." Bioacoustics 10 (1999): 203.
Francescoli, Gabriel, and Carlos A. Altuna. "Vibrational Communication in Subterranean Rodents: The Possible Origin of Different Strategies." Evolution of Communication 2(1998): 217.
Pearson, Oliver P., and Miguel I. Christie. "Los Tuco-tucos (género Ctenomys) de los Parques Nacionales Lanin y Nahuel Huapi, Argentina." Historia Natural 5 (1985): 337.
Zenuto, Roxana R., Aldo I. Vassallo, and Cristina Busch. "A Method for Studying Social and Reproductive Behaviour of Subterranean Rodents in Captivity." Acta Theriologica 46(2001): 161.
Other:Gabriel Francescoli's Webpage. .
Gabriel Francescoli, PhD Graciela Izquierdo, PhD
[Article by: Bettina Tassino, MSc; Carlos Altuna, Lic]
