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Ctenomys pearsoniPearson's tuco-tuco

By Kathryn Silverstein

Geographic Range

Ctenomys pearsoni is found in the Southern Departments of Uruguay (Altuna et. al. 1998) as well as the Entre Rios Province. (Lessa and Langguth, 1983) (Altuna, et al., 1998; Lessa and Langguth, 1983)

Habitat

Pearson's tuco-tucos live in coastal sandy areas or dunes, although individuals have been found living as far as 500 meters from sandy soil (Altuna et. al. 1999). Typically, these animals prefer living along the edge of, or near the mouth of, rivers (Lessa and Langguth 1983). (Altuna, et al., 1999; Altuna, 1983; Lessa and Langguth, 1983)

Pearson's tuco-tucos live individually in subterranean burrows that are typically composed of a main gallery with other galleries and chambers that extend laterally from it (Altuna, 1983). Burrows usually have multiple mouths, which are kept closed most of the time; this keeps the humidity inside the burrow fairly constant, at around 92.65%. Pearson's tuco-tucos will only open burrowd for ventilation or when exiting to forage for food. The length, depth and layout of burrows varies and is determined, in part, by the hardness of the substrate and other topographic features of the location. Lengths of galleries have been recorded from 7.10 meters up to 24.40 meters (Altuna 1983). The diameter of a gallery is only slightly larger than the animal that lives there. The burrows of adult females were found to be larger than those of adult males and the burrows of juveniles were found to be shorter than those of adults (Altuna 1999). (Altuna, et al., 1999; Altuna, 1983)

Physical Description

Pearson's tuco-tucos have an average length (body plus tail) of 19 cm and an average weight of 200 g. They have a reddish brown pelage with a white collar under the neck and white patches on the sides of the neck (Grizmek, 2003). They are similar to other species of Ctenomys in appearance, however C. pearsoni adult males possess a distinctive penis morphology that allows them to be distinguished from other members of the genus. Relative to other species of Ctenomys, C. pearsoni has the most distinctive bacular dimensions: wider, shorter and better defined than other species (Balbontin et. al. 1996). The baculum is paddle-shaped and single tipped (Altuna and Lessa 1985). The baculum also has a pair of spiny bulbs with varying numbers of spikes and the sperm are symmetrical, morphological traits also seen in C. dorbignyi, C. perrensi and C. roigi. Ctenomys pearsoni may have developed such a distinct baculum in response to selection pressure for reproductive isolation from other populations of spike bearing Ctenomys living close by (Balbontin et. al. 1996). ("Ctenomys pearsoni", 2003; Altuna and Lessa, 1985; Balbontin, et al., 1996; Lessa and Langguth, 1983)

The incisors of C. pearsoni are more protodont than those of C. torquatus and C. talarum, but are not as protodont as the incisors of C. riongegrensis and C. minutus (Lessa and Langguth 1983). (Lessa and Langguth, 1983)

A population of Ctenomys with a morphology similar to C. pearsoni has been found in Southern Uruguay east of the Santa Lucia river in the Departments of Carrasco, Salinas and Maldonado, but those animals do not have the same karyotype (Lessa and Langguth 1983). (Lessa and Langguth, 1983)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    200 g
    7.05 oz
  • Average length
    19 cm
    7.48 in

Reproduction

Courtship and copulation occur in the burrow and during this brief period males and females live together (Altuna, 1991). The behavior of C. pearsoni during courtship involves males and females communicating through acoustic and tactile signals that tell males when females are ready to copulate and help to calm females, who are ordinarily very aggressive and territorial (Francescoli, 1998). While females are sexually mature and mate within their first year, males do not. This may be because females are exceptionally aggressive when they are in estrus and force juvenile males to take a submissive position when they are together (Tassino, 1992). Reproductive structures, such as the baculum, with its spiny bulbs and spikes, are not fully developed in males under a year old (Altuna and Lessa, 1985). This reduces a juvenile male's ability to court and copulate with females as these structures most likely play an important role in stimulating females and inducing ovulation. Mating in C. pearsoni involves a series of alternating copulation and intercopulation periods. A copulation period is initiated when the male mounts the female and ends when the male dismounts, starting a new intercopulation period during which the male will court the female again. During a copulation period, males alternate between rapid pelvic thrusting and deep intromission with multiple ejaculations (Altuna et. al. 1991). (Altuna and Lessa, 1985; Altuna, et al., 1991)

Ctenomys pearsoni breeds once yearly. The breeding season occurs in the winter months of May, June, and July. Litter size ranges from 2 to 4, young are weaned in 32 to 40 days, and the young become independent at approximately 2 months of age.

  • Breeding interval
    Pearson's tuco-tucos breed once yearly.
  • Breeding season
    The breeding season for Pearson's tuco-tucos takes place during the winter months of May, June, and July.
  • Range number of offspring
    2 to 4
  • Range weaning age
    32 to 40 days
  • Average weaning age
    34.9 days
  • Average time to independence
    2 months

Ctenomys pearsoni exhibits highly motivated maternal behavior postpartum. Mothers build nests for their young and, following parturition, they spend more than 80% of their time in the nest with their pups. Mothers provide warmth for their babies by huddling in the nest with them. They also supply food, both milk and solid food they have collected and brought into the burrow. Mothers also groom the pups and will seek out and return to the nest any pups that may have wandered off. As pups become more mobile and start to wander more frequently, around the 2nd week of lactation, maternal behaviors begin to decline. By the 4th week the mother is still sleeping and huddling in the nest with her young and grooming them but now the pups help with the maintenance of the nest and food gathering. After the fifth week of lactation the mother leaves the pups alone more often, no longer restricts them from wandering and begins to reject their attempts to nurse (Pereira, 2006). However, even after the young are weaned they continue to remain with their mother for another 3 to 4 weeks. At that point they disperse, typically to the edges of the population, and dig their own burrow (Altuna et. al. 1999). (Altuna, et al., 1999; Pereira, 2006)

Behaviors exhibited by pups appear to play an important role in stimulating care-giving behaviors in their mother in that changes in pup development induce corresponding changes in maternal activities. Studies of C. pearsoni females in captivity reveal that mothers are willing to care for alien pups as well as their own pups. This is despite the fact that mothers were able to distinguish their pups from alien pups based on olfactory cues. Since this ability to identify pups is not used to determine which pups the mother is willing to care for, it most likely developed as a strategy to counter the extremely territorial and aggressive nature of C. pearsoni females. As pups get older and begin to wander in and out of burrows on their own, the ability to recognize their own pups' scent prevents females from attacking their young when they are returning to the nest (Pereira, 2006). (Pereira, 2006)

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

Lifespan/Longevity

The lifespan of C. pearsoni is unknown.

Behavior

Pearson's tuco-tucos are fossorial, solitary rodents. They leave their burrows only to collect food and to disperse from the mother's burrow (Pereira 2006). The only time two adults share a burrow is for a very brief period during breeding season (Altuna et. al. 1991). These animals are very territorial and aggressive. They are vocal animals and will use vocalizations to defend their territory and warn off intruders (Francescoli 2002). If confronted with an intruder in their burrow, they will attack (Francescoli, 2005). (Altuna, et al., 1991; Francescoli, 2002; Francescoli, 2005; Pereira, 2006)

Home Range

Home range sizes of Pearson's tuco-tucos have not been reported.

Communication and Perception

Tuco-tuco's are very vocal animals; they use many different types of vocalizations to communicate everything from aggression to sexual receptivity. At least 4 different types of vocalizations made by C. pearsoni have been classified. "S signals" play a very important role in the life of C. pearsoni. These signals are extremely structured, repeating, low-pitched calls that are often emitted so loudly that they can be heard outside the animal's burrow even if it is closed. They can also travel through the soil up to 6 meters away from the source. S signals are most likely used to defend territories, and prevent other individuals from building overlapping burrows. These vocalizations also can communicate sexual information among individuals in a population (Francescoli, 2005). There are also vocalizations known as "G signals", which are used during acts of aggression, such as occurs between two males who are both seeking access to the burrow of a receptive female (Altuna et. al. 1999). "C signals" are used by a female to indicate to an interested male that she is ready to mate. It has been hypothesized that because mounting attempts by the male are usually made after hearing a C signal (Francescoli, 2005), they may serve the same purpose as lordosis, which is a behavior not done by C. pearsoni females. Vocalizations are also important in the relationship between a mother and her pups. High frequency calls, known as RN signals, are made by pups who have wandered from the nest and result in the mother finding and retrieving them. (Francescoli, 2005).

To hear samples of C. pearsoni vocalizations please follow these links: "S signal": http://eto.fcien.edu.uy/sonidos/tuc.wav "C signal": http://eto.fcien.edu.uy/sonidos/c-all.wav "RN signal": http://eto.fcien.edu.uy/sonidos/crias3.wav (Altuna, et al., 1999; Francescoli, 2005)

Food Habits

Ctenomys pearsoni is an herbivorous generalist that bases its food selection more on the abundance and accessibility of a food than its nutritive value or water content. Laboratory studies showed that while C. pearsoni ate all species of plants provided, the two species of plants that make up almost 84% of its habitat's vegetal cover, Cynodon dactylon and Panicum racemosum, were the favorites. Also, field research has found chambers containing large amounts of these plants in the burrows of C. pearsoni (Altuna et. al. 1999). (Altuna, et al., 1999)

Ctenomys pearsoni exhibits a number of behaviors related to obtaining and eating food. These animals do not eat their food above ground but instead emerge from the burrow briefly to cut and gather grasses and forbs. When returning to the burrow with food, C. pearsoni walks or runs backward using its tail to navigate. Once inside the burrow, grasses are held in one or both forepaws and shaken up and down in sequences of 4 to 18 movements at a high velocity (.16 shakes per second). This behavior is an effective method for removing dirt and soil from food and is used on wet, dry and dirty grasses alike (Altuna et. al., 1998). Similar food shaking behavior can be seen in other subterranean rodents such as Cryptomys damarensis (Bennet, 1990) and Geomys bursarius (Vaugn, 1966). Once the food is clean, large items are held with both forepaws and the incisors are used to twist and cut them into smaller pieces (Altuna et. al., 1998). (Altuna, et al., 1998)

Ctenomys pearsoni practices autocoprophagy. This helps it obtain maximum nutritive value from its food and is especially important in the retention of water because C. pearsoni does not drink free water. Reingestion of feces most often takes place during resting periods or between feeding episodes. A special posture is adopted so that an animal is able to take fecal pellets with its lips and incisors instead of using its forepaws. The fecal pellets are chewed before they are swallowed (Altuna et. al., 1998). Chambers containing feces that are similar to those containing cut pieces of vegetation have been found in C. pearsoni burrows (Altuna et. al., 1999). (Altuna, et al., 1999)

A unique feature of C. pearsoni is the size and mass of its caecum, where microbial fermentation of cellulose and pectin take place. The caecum in C. pearsoni weighs around 30% of the animal's total body weight and occupies the entire breadth of the abdomen, making it the most developed among hystricognath rodents (Altuna et. al., 1998). (Altuna, et al., 1998)

  • Plant Foods
  • leaves
  • wood, bark, or stems
  • Other Foods
  • dung

Predation

Juveniles are particulary vulnerable to predation by birds of prey, especially owls (Strigiformes), when they leave their mother's burrows and must migrate to the edges of the population to construct their own burrow (Altuna et. al. 1999). Pearson's tuco-tucos are cryptically colored and otherwise remain in or near their burrows for fast escape from predators. (Altuna, et al., 1999; Altuna, et al., 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The role played by Ctenomys pearsoni in its ecosystem has not been studied. They are likely to affect plant communities through their feeding habits and may help to aerate the soil and provide burrows to other animals.

Economic Importance for Humans: Positive

These animals have no obvious positive economic impact on humans, except for their roles as members of healthy, native ecosystems.

Economic Importance for Humans: Negative

These animals have no obvious negative economic impact on humans.

Conservation Status

Presently, urbanization poses the greatest risk to Ctenomys pearsoni. Many small populations of C. pearsoni that were living in areas where roads, fences, or train tracks were installed, have gone extinct as a result of prolonged inbreeding due to being isolated from other populations by these man-made barriers (Altuna, et. al. 1999). (Altuna, et al., 1999)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Kathryn Silverstein (author), Michigan State University, Barbara Lundrigan (editor, instructor), Michigan State University.

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.

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.

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.

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

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

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

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.

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

2003. Ctenomys pearsoni. Pp. 428-429 in M McDade, ed. Grzimek's Animal Life Encyclopedia, Vol. 16/Mammals V, 2nd Edition. Detroit: Gale.

Altuna, C. 1983. Sobre la Estructura de las Construcciones de Ctenomys pearsoni Lessa y Langguth, 1983 (Rodentia, Octodontidae). Resumenes Comunicaciones Jornadas de Ciencias Naturales, 3: 70-72.

Altuna, C., L. Bacigalupe, S. Corte. 1998. Food-handling and Feces Reingestion in Ctenomys pearsoni (Rodentia, Ctenomyidae) from Uruguay. Acta Theriologica, 43: 433-437.

Altuna, C., G. Francescoli, G. Izquierdo. 1991. Copulatory Pattern of Ctenomys pearsoni (Rodentia, Octodontidae) from Balneario Solis, Uruguay. Mammalia, 55/2: 316-318.

Altuna, C., G. Francescoli, G. Izquierdo, B. Tassino. 1999. Ecoetologia y Conservacion de Mamiferos Subterraneos de Distribucion Restringida: el Caso de Ctenomys pearsoni (Rodentia, Octodontidae) en el Uruguay. Etologia, 7: 47-54.

Altuna, C., G. Izquierdo, B. Tassino. 1983. Analisis del Comportamiento de Excavacion en Dos Poblaciones del Complejo Ctenomys pearsoni (Rodentia Octodontidae). Boletin de la Sociedad Zoologica del Uruguay, 8: 275-282.

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

Balbontin, J., S. Reig, S. Moreno. 1996. Evolutionary Relationships of Ctenomys (Rodentia: Octodontidae) from Argentina Based on Penis Morphology. Acta Theriologica, 41/3: 237-253.

Francescoli, G. 2002. Geographic Variation in Vocal Signals of Ctenomys pearsoni. Acta Theriologica, 47/1: 35-44.

Francescoli, G. 2001. Vocal Signals from Ctenomys pearsoni Pups. Acta Theriologica, 46/3: 327-330.

Francescoli, G. 2005. "Ctenomys" (On-line). Accessed March 21, 2007 at http://eto.fcien.edu.uy/gaboeng.htm.

Lessa, E., A. Langguth. 1983. Ctenomys pearsoni n. sp. (Rodentia, Octodontidae), del Uruguay. Resumenes Comunicaciones Jornadas de Ciencias Naturales, 3: 86-88.

Pereira, M. 2006. Nonselective Maternal Bonding but Pup Recognition in the Subterranean Rodent Ctenomys pearsoni. Journal of Comparitive Psychology, 120/4: 411-415.

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