Spalacopus cyanuscoruro

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Geographic Range

Spalacopus cyanus, one of two species known as "cururos", is endemic to Chile. Its range extends along the Chilean coast from Caldera (27 degrees S) to Quirihue (36 degrees S) and in the Andes from Alicahue (32 degrees S) to Los Cipreses (34 degrees S) up to elevations of 3,000 meters. The species also sparsely inhabits the Intermediate Depression (Contreras and Gutierrez 1991, Hanney 1975, Walker 1975).

Habitat

Spalacopus cyanus inhabits arid costal grassland, stabilized coastal dune land, Acacia savannah, and alpine Andean grassland. These habitats are generally arid and are characterized by scrubby herbaceous vegetation with little woody plant cover (Contreras and Gutierrez 1991, Hanney 1975, Vaughan et al. 2000).

Physical Description

Large, protruding, curved upper incisors, and upper molars possessing reentrant folds that do not meet in the middle of the tooth distinguish this species from its close relatives. The eyes are quite large for a fossorial species. The tail is scaly, cylindrical, and hairless, and is 40 to 50 mm in length. Excluding the tail, the total body length of the species is 140-160 mm (Hanney 1975, Walker 1975).

The pelage of this stocky species is thick, glossy, and soft. Pelage coloration ranges from uniform black to brownish black. Spalacopus cyanus have dark gray feet, the digits of which possess relatively small claws for a fossorial species (Hanney 1975, MacDonald 1987, Walker 1975).

  • Range mass
    0.080 to 0.120 kg
    0.18 to 0.26 lb
  • Average basal metabolic rate
    0.561 W
    AnAge

Reproduction

Copulation lasts around 15 seconds and culminates with a cry emitted by the female. The gestation period is around 77 days, and females can produce two litters in a breeding season, which takes place from July until January. Breeding peaks in mid-summer (Bengall et al. 1999).

In captivity, the litter size ranges from 2-5 (mean of 3.5) neonates. Dependent on their mothers, newborns are born with closed eyes and thin pelage. The eyes open around 4 days after birth and weaning occurs around 60 days after birth (Bengall et al. 1999).

Based on colony age and sex ratios, the mating system of Spalacopus cyanus is likely polygynous, with males dispersing earlier than females. Late dispersal and overlap of two or more generations in a colony is probable. Only one sexually active male remains in a colony (Bengall et al. 1999).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Range number of offspring
    2.000 to 5.000
  • Average number of offspring
    2.4
    AnAge
  • Average gestation period
    77 days
  • Average weaning age
    60 days

Lifespan/Longevity

Behavior

Spalacopus cyanus are colonial, nomadic, and entirely fossorial. Complex burrows are dug with the forelimbs and greatly enlarged front incisors. Loosened earth is expelled from the mouth of the burrow by the large hind feet. Burrows are 50-70 mm in diameter and are located 100-120 mm below the surface of the ground. Mean winter burrow temperature is around 4.0 C for coastal populations and around 11 C for mountain populations. Burrow openings are spaced about 1 m apart. Burrow excavation is very rapid. Upon moving into a new area, one colony dug 250 burrow openings in only three days. This species is most active around midday and is strictly diurnal (Contreras 1986, Contreras and Guierrez 1991, Hanney 1975, Vaughan et al. 2000, Walker 1975).

Colonies consist of around fifteen members and multiple colonies exist in close proximity. The burrows of adjacent colonies usually interconnect and these interconnected burrow systems may extend continuously for many kilometers (Hanney 1975).

Once a colony has exhausted the food supply of an area, the colony relocates to a new area where undisturbed vegetation is present. The activity of the colony varies with the availability of food (Walker 1975).

It has been speculated that the nomadic behavior and foraging habits of Spalacopus cyanus allow one colony to persist in the same areas for an extended time period. In one study along the coast of Chile, total average plant biomass was 60% greater in areas with Spalacopus cyanus burrows than in areas without this species' burrows. According to this study, Spalacopus cyanus reduced the number of large geophyte bulbs and facilitated the germination of new bulbs. The nomadic lifestyle of Spalacopus cyanus allows new bulbs to grow in an abandoned area, to which the colony will eventually return (Contreras and Gutierrez 1991, Vaughan et al. 2000, Walker 1975).

Unfamiliar individuals are very antagonistic and aggressive. Rapid tail wagging, teeth-grinding, staring contests, and growling are typical antagonistic behavior. Unfamiliar individuals fight violently until one individual is displaced or lies on its back and "gurgles" in submission as the dominant individual sniffs the submissive individual's anogenital area (Begall et al. 1999).

Spalacopus cyanus are quite vocal. Most vocalizations consist of a sequence of three or four musical trills, each lasting around five seconds and separated from the following trill by around three seconds of silence. Vocalizations are made at burrow mouths when these rodents are startled (Begall et al. 1999, Vaughan et al. 2000, Walker 1975).

This species of cururo also exhibits behavioral thermoregulation. At low ambient temperatures, individuals curl up, reducing surface-to-volume ratios and thus conserving heat. At high ambient temperatures, individuals lie on their sides or back to maximize surface-to-volume ratios and facilitate heat loss. Presumably because of high burrow humidity, Spalacopus cyanus do not spread saliva on their fur. Many rodents use saliva to cool their bodies through evaporation (Contreras 1986).

Communication and Perception

Food Habits

While Spalacopus cyanus feed on forbs, grass shoots, bark, and cacti, the principal food of this species is geophyte bulbs such as huilli (Leucocoryne ixioides, Liliaceae). Coruros feed entirely underground. Presumably, Spalacopus cyanus visually locate areas where food is likely to be present after surveying the surrounding landscape from the mouths of their burrows. They then excavate shallow feeding tunnels towards these areas. This species is known to store bulbs and tubers within its burrows for winter consumption (Contreras and Gutierrez 1991, MacDonald 1987, Vaughan et al. 2000, Walker 1975).

  • Primary Diet
  • herbivore
    • eats sap or other plant foods
  • Plant Foods
  • roots and tubers

Economic Importance for Humans: Positive

Local people often raid this species' winter stores of bulbs and tubers for food (Walker 1975).

Economic Importance for Humans: Negative

none

Conservation Status

Other Comments

Individuals of this species from higher elevations are generally larger than individuals from lower elevations, and sexual dimorphism is more pronounced in populations from lower elevations (Contreras 1986).

The morphology of the glans penis and the size and shape of the baculum of Spalacopus cyanus are derived characters. It has been suggested that this species is an isolated remnant of an ancient radiation (Contreras et al. 1993).

The rather specialized diets and nomadic lifestyles exhibited in the genus Spalacopus restrict rapid speciation. Such speciation is seen in the equally fossorial and more sedentary family Ctenomyidae (Vaughan et al 2000).

There are two members of the genus Spalacopus: Spalacopus tabanus and Spalacopus cyanus. Spalacopus tabanus is larger than S. cyanus and inhabits southern Chile (Walker 1975).

The family Octodontidae first appears in the fossil record in the lower Oligocene in South America and in the Pleistocene in the West Indies (Vaughan et al. 2000, Walker 1975).

Contributors

Gerhard Mundinger (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, 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

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.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

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.

herbivore

An animal that eats mainly plants or parts of plants.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

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.

tactile

uses touch to communicate

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.

References

Begall, S., H. Burda, M. Gallardo. 1999. Reproduction, postnatal development, and growth of social coruros, Spalacopus cyanus (Rodentia: Octodontidae), from Chile. Journal of Mammalogy, 80(1): 210-217.

Contreras, L. 1986. Bioenergetics and distribution of fossorial Spalacopus cyanus (Rodentia): Thermal stress, or cost of burrowing. Physiological Zoology, 59(1): 20-28.

Contreras, L., J. Gutierrez. 1991. Effects of the subterranean herbivorous rodent Spalacopus cyanus on herbaceous vegetation in arid coastal Chile. Oecologia, 87: 106-109.

Contreras, L., J. Torres-Mura, A. Spotorno, F. Catzeflis. 1993. Morphological variation of the glans penis of South American Octodontid and Abrocomid rodents. Journal of Mammalogy, 74(4): 926-935.

Hanney, P. 1975. Rodents: Their Lives and Habits. New York, New York: Taplinger Publishing Company.

MacDonald, D. 1987. The Encyclopedia of Mammals. New York, New York: Facts on File Publications.

Vaughan, T., J. Ryan, N. Czaplewski. 2000. Mammalogy, 4th Edition. Fort Worth, Texas: Saunders College Publishing.

Walker, E. 1975. Mammals of the World. Baltimore, MD: The Johns Hopkins University Press.