Spalacopus cyanus
coruro

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).

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).

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).

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).

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).

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

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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).