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Ctenomys conoveriConover's tuco-tuco

By Katie Brashear

Geographic Range

Conover's tuco-tucos are endemic to the Chaco in both Bolivia and Paraguay, occurring at an altitude of 250 m. They are found from 20 degrees S to 23 degrees S and 60 degrees to 63 degrees. This species has one of the smallest ranges of the thirty-eight currently recognized species in the genus Ctenomys. As a genus, tuco-tucos are considered to exhibit considerable ecologic plasticity. The fossil record dates back to the Pliocene in this range. Currently, it is thought that a vicariant event cannot explain present distributions. (Cook and Yates, 1994; Eisenberg and Redford, 1992; Nowak, 1991)

Habitat

Ctenomys concoveri is a primarily fossorial species. Conover's tuco-tucos are found in areas of sandy or loamy soils. In the Paraguayan Chaco, the landscape is primarily savannah grassland and shrub forest. The shrub forest is characterized by thorny bushes, shrubs, and cacti, with scattered trees up to 13 m high. The dominant species in the forest include Prosopis ruscifolia, a thorny legume, and Opuntia sp. Much of the grassland is under severe agricultural pressure. (Brooks, 2002)

  • Average elevation
    250 m
    820.21 ft

Physical Description

Conover's tuco-tucos are large for this genus, and can reach weights in excess of 1 kg. This species strongly resembles North American pocket gophers (Geomyidae). As a fossorial species, they have a robust and cylindrical body, large head, short and sparsely haired tail, and short, muscular neck and forelimbs. The eyes are medium-sized and positioned to enable these animals to look out of the burrow without exposing the whole body. The external ears are very small, another adapation to fossorial living. The forelimbs are slightly shorter than the hindlimbs, and all digits have claws. The claws on the forefeet are the longest, and are used for loosening packed earth.

The skin seems loosely applied to the body, possibly making it easier for these animals to turn around in narrow burrows. The soles of the hind feet are equipped with comb-like bristles, composed of hair fringes, and are used to groom dirt from the fur. (Eisenberg and Redford, 1992; Nowak, 1991)

Conover's tuco-tucos have a tan dorsum with a faint mid-dorsal line. The top of the head is a gray-brown, lightening to flecking on the back of the head. The cheeks are a brownish-yellow, and touches of white surround the mouth and chin. The ventrum is also a light yellow. Generally, the fur is thick and long. (Eisenberg and Redford, 1992; Nowak, 1991)

Like other Ctenomys, Conover's tuco-tucos have a broad, flattened skull. They lack a sagittal crest but have prominent ridges along the parietals. The zygomatic arches are strongly bowed outward, and the jugal bone does not contact the lacrimal bone. They are equipped with large auditory bullae and large paroccipital processes. The dental formula is 1/1, 0/0, 1/1, 3/3 = 20. Ctenomys concoveri is noted for prominent broad and heavy proodont incisors; each of the anterior surfaces has an inner and outer wide lateral groove and three shallow, narrow median grooves. These incisors, covered by a bright orange enamel, are used to gnaw roots when digging. This species also has kidney-shaped hypsodont molars for chewing vegetation, with the last molar being reduced. (Eisenberg and Redford, 1992; Myers, 1999)

Although males are reported to be larger than females, the following measurements apply to both sexes. Total length of these animals ranges from 338 to 442 mm (average = 403.3 mm); head and body length varies from 245 to 328 mm (average = 293.3 mm); tail length ranges between 93 and 137 mm (average = 110.0 mm); hindfoot length is between 52 and 62 mm (average = 58.0 mm); and ear length (notch to tip) is between 10 and 16 mm (average = 13.4 mm). The average adult weighs about 900 grams. (Eisenberg and Redford, 1992)

  • Sexual Dimorphism
  • male larger
  • Average mass
    0.900 kg
    1.98 lb
  • Range length
    338 to 442 mm
    13.31 to 17.40 in
  • Average length
    403.3 mm
    15.88 in

Reproduction

Sexual size dimorphism and enlarged testes are observed in this and other Ctenomys species, suggesting polygynyis the primary mating system. (Nowak, 1991)

Female C. conoveri are monoestrus, bearing one litter per year. They construct lined nest chambers, typically below the level of the main tunnel. (Myers, 1999)

Gestation length is not available for this species, but other species in the genus Ctenomys range from about 102 to 120 days. Litters range in size from 1 to 7 young. Young of this genus may be born at varying levels of altriciality. Some young are precocious, coming out fully furred and looking like miniature adults. Others are only slightly furry at birth, and may have their eyes closed. The condition of C. concoveri at birth has not been reported. (Nowak, 1991)

Young of Ctenomys talarum are reportedly able to fend for themselves by about 10 days of age, even though they are not the most precocious members of their genus at birth. Nursing is said to continue for 5 weeks, and sexual maturity is reached sometime around 8 months of age, for both males and females. It is likely that C. concoveri is similar. (Nowak, 1991)

  • Breeding interval
    Conover's tuco-tuco breeds once a year.
  • Breeding season
    The exact breeding season for these animals has not been reported.
  • Average gestation period
    203 days

Ctenomys conoveri has altricial young. The females are generally responsible for care and feeding of the young. Male parental care has not been reported. (Nowak, 1991)

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

The mean lifespan in the wild for Conover's tuco-tucos is probably less than three years, as they are an important prey species in the Chaco. (Nowak, 1991; Brooks, 2002)

  • Average lifespan
    Status: wild
    3 years

Behavior

Conover's tuco tucos are noted for building complex, branching tunnel systems, which include nesting chambers and other specialized chambers for food storage. At times the actual burrow openings are plugged, perhaps to deter predators. Most tunnels average 14 m long, 5 to 7 cm wide, and 30 cm below the surface. As a fossorial species, C. conoveri uses its strong incisors and hind limbs to excavate burrows. They most often dig during daylight hours, especially early morning and late afternoon. When threatened, they may back rapidly into the burrow, using their almost hairless tail as a sensory apparatus. (Myers, 1999)

Home Range

The size of the home range of this species has not been reported.

Communication and Perception

Conover's tuco-tucos, like all other tuco-tucos, earned their common name in part for the alarm call emitted by males due to territoriality or fear. The calls last 10 to 20 seconds, beginning at a slow rate and increasing throughout. In reality, the sound is more of a "tloc tloc tloc" than a "tuco tuco." (Nowak, 1991)

Although details are not available, it is also likely that these animals communicate with one another through visual signaling. They also are likely to have tactile communication, especially between mates, parents and offspring, and rivals.

Food Habits

Ctenomys conoveri is entirely vegetarian, feeding on roots, stems, and grasses of the Chacoan region. Its preference for plant material makes it a pest because of damage to cultivated crops--much like the North American pocket gophers (Geomyidae). It builds separate food burrows for food storing. (Nowak, 1991)

  • Plant Foods
  • leaves
  • roots and tubers

Predation

As rodents in the Chacoan ecosystem, C. conoveri serve as an important food item for many predators, including owls, diurnal raptors, carnivorous mammals such as the maned wolf and the pampas fox, and feral cats. The males are aposematic, meaning that they elicit alarm calls as an antipredatory adaptation; additionally, the placement of the eyes allows these animals to look out of their burrows without exposing the rest of the body. (Brooks, 2002; Myers, 1999)

Ecosystem Roles

The strong foraging habits of Conover's tuco-tucos have been crucial to maintaining habitat openings and providing regrowth forage for wild and domestic ungulates; They also aerate the soil through their burrowing behaviors. They present vital habitat via burrows to many species of mammals, lizards, toads, invertebrates, and, at times, birds. They are also a prey species for a viariety of raptors and carnivorous mammals. (Brooks, 2002; Myers, 1999)

Economic Importance for Humans: Positive

Although often unrecognized, Conover's tuco-tucos do provide positive services for humans. Through their burrowing habits, they maintain wildlife habitat, which assists resource managers and ecotourists. Their excrement also provides a fertilizer for the soil and crops. Similarly, their burrowing habits may aid agriculturists in aerating and maintaining the soil. Their foraging habits oftentimes stimulate faster plant growth rather than halting it. More research is being conducted on them as interest in the Chacoan ecosystem and Ctenomys species continues to grow. They are also becoming more commonly listed on many pet trade web pages. (Myers, 1999)

Economic Importance for Humans: Negative

Similar to the prairie dog controversy in the American west, Conover's tuco-tucos create burrows that damage agricultural and graze areas. Additionally, as herbivores, they have done a lot of agricultural damage through their preference for roots, stems, and grasses. Many people believe their burrows result in injury and death for livestock, while others feel their foraging habits outcompete domestic livestock. (Myers, 1999; Brooks, 2002)

  • Negative Impacts
  • crop pest

Conservation Status

Conservation efforts for this taxa are frought with taxanomic dispute and disregard for them by ranchers. Differentiation of the genus Ctenomys was historically based on pelage and morphological differences; it is now shifting to DNA and molecular sequencing, due to their substantial chromosomal variation. This species is highly understudied and misunderstood by local inhabitants. They are often persecuted by people, and desire and funding to study this species is often low. Conover's tuco tucos are not listed by CITES or IUCN. (Cook and Yates, 1994; Nowak, 1991)

Other Comments

Old classification of this species placed it in the genus Chacomys. (Nowak, 1991)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Katie Brashear (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

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

agricultural

living in landscapes dominated by human agriculture.

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.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

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

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.

fertilization

union of egg and spermatozoan

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.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynous

having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

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

social

associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in

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.

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.

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

Barlow, J. 1969. Observations on the Biology of Rodents in Uruguay:Science Contribution Number 75. Royal Ontario Museum of Life Science.

Brooks, D. 2002. "Chaco (NT0210)" (On-line ). World Wildlife Fund. Accessed 12/09/02 at http://www.worldwildlife.org/wildworld/profiles/terrestrial/nt/nt0210_full.html.

Cook, J., T. Yates. 1994. Systematic relationships of the Bolivian tuco-tucos, genus *Ctenomys*. Journal of Mammalogy, 75: 583-599.

Eisenberg, J., K. Redford. 1992. Mammals of the Neotropics: Volume 2. Chicago: Univeristy of Chicago Press.

Myers, P. 1999. "Ctenomyidae" (On-line ). Animal Diversity Web. Accessed 10/16/02 at http://animaldiversity.ummz.umich.edu/chordata/mammalia/rodentia/ctenomyidae.html.

Nowak, R. 1991. Walker's Mammals of the World, Fifth Edition. Baltimore: Johns Hopkins University Press.

Wilson, D., D. Reeder, C. Woods. 1993. Mammal Species of the World: a Taxanomic and Geographic Reference; Second Edition. Washington, DC: Smithsonain Institution Press.

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