21.
Bolivian Chinchilla Rat
(Abrocoma boliviensis)
CR
Overview
Chinchilla rats are similar in appearance to both chinchillas and rats, hence the common name. Their fur is long, dense and soft and almost as prized as that of true chinchillas, while their proportionately longer head and ears give them a more rat-like appearance. The Bolivian chinchilla rat is the smallest of the three living Abrocoma species, and is distinguishable by its longer, hairier tail. It lives in burrows and is associated with rocky areas within cloud forest. The main threats appear to be from habitat loss and fragmentation as the forest is cleared for cattle pasture and human colonisation.
Urgent Conservation Actions
Habitat protection and surveys to identify the location of key populations.
Distribution
Restricted to central Bolivia
Evolutionary Distinctiveness
Order: Rodentia
Family: Abrocomidae
The Caviomorpha (South American hystricognath rodents) comprises 13 extant New World rodent families grouped into four superfamilies: Erethizontoidea (New World porcupines), Cavioidea (guinea pigs), Chinchilloidea (chinchillas) and Octodontoidea (spiny rats). These taxa suddenly appeared and diversified in South America in the Early Oligocene (31 Myr ago) probably following one or more transatlantic migrations from Africa.

Modern octodontoids are thought to have originated 13-18 million years ago, during a period of climatic change in South America that may have driven the evolution of new species. The Octodontoidea is now the most diversified caviomorph clade, with a first radiation having produced the three extant families Abrocomidae, Octodontidae and Ctenomyidae and a fourth lineage, which is thought to have subsequently diversified into Capromyidae (hutias), Myocastoridae (coypu), and Echimyidae (spiny rats).

The family Abrocomidae (chinchilla rats) is the most basal lineage within the superfamily Octodontoidea. It contains 2 genera comprised of 4 extant species: A. boliviensis, Abrocoma bennetti, A. cinerea, and Cuscomys ashaninka. The 3 currently recognized species in Abrocoma are distributed in west-central South America from southern Peru southward to central Argentina.

A. boliviensis was described as a new species by Glanz and Anderson (1990), based on 2 specimens that had been collected in 1926 and 1955 but that had never been identified to species status. It is one of nine rodent species known only occur in Bolivia.
Description
Size: 
Head and body length: 170-178 mm (based on 2 specimens)
Weight: 225 – 300 g
Chinchilla rats are so-named because of the similarity of their long, dense, soft fur to that of chinchillas. Fur colouration is silvery grey above and white or yellowish below. The Bolivian chinchilla rat has a rat-like body with a long pointed nose, large eyes and large rounded ears. The limbs are short. The forefeet have four digits and the hindfeet have five. Stiff hairs project over the claws of the three middle toes of the hind foot, forming combs that are probably used to remove parasites and/or dirt and groom. A. boliviensis is the smallest of the extant Abrocoma species and is distinguishable by their longer, hairier tails.
Ecology
Very little is known about the ecology of this little-known rodent species. It is thought to live in burrows and have a vegetarian diet comprising many kinds of plant material. In common with other hystricognath rodents, it gives birth to precocial young – young that are relatively well-developed and mobile from the moment of birth – presumably after a lengthy gestation period.
Habitat
Individuals have been found in cloud forest at an elevation of 1,800 m above sea level. They tend to be associated with rocky areas, and some researchers have suggested that they may be specialised to this habitat type.
Distribution
This species is known only from the vicinity of the type locality near the Comarapa river valley in the province of Manuel M. Caballero, Santa Cruz department, Bolivia. Its currently known range is less than 100 km², although it may possibly range more widely.
Population Estimate
Unknown.
Population Trend
Decreasing.
Status
Classified as Critically Endangered (CR B1ab(i,ii,iii)) on the 2010 IUCN Red List of Threatened Species.
Threats
This species appears to have been unaffected by the fur trade which targeted other species of chinchilla rat in the past. The main threat appears to be from habitat loss and degradation. Its range is divided by a road along which human colonisation is occurring. This, together with the clearance of cloud forest for cattle pasture, is fragmenting the species’ habitat.
Conservation Underway
This species is not known from any protected areas nor are there any targeted conservation actions in place.
Conservation Proposed
There is an urgent need to protect the distinct area of Comarapa. Further research is also needed in this area to try to find additional populations.
References
Barrthlott, W.,Winiger, M.and Biedinger, N. 2001. Biodiversity: a challenge for development research and policy. Springer – Verlag, Berlin, Heidelberg. P281

Braun, J. K. & Mares, M. A. 2002. Systematics of the Abrocoma cinerea species complex (Rodentia: Abrocomidae), with a description of a new species of Abrocoma. Journal of Mammalogy 83(1): 1-19.

Dunnum, J., Vargas, J. & Bernal, N. 2008. Abrocoma boliviensis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 15 November 2010.

Glanz, W. E. & Anderson, S. 1990. Notes on Bolivian Mammals. 7. A New Species of Abrocoma (Rodentia) and Relationships of the Abrocomidae. American Museum Novitates 2991.

Honeycutt, R. L., Rowe, D. L. and Gallardo, M. H. 2003. Molecular systematics of the South American caviomorph rodents: relationships among species and genera in the family Octodontidae. Molecular Phylogenetics and Evolution 26: 476–489.

Nowak, R. M. 1999. Walker’s Mammals of the World. Sixth edition. The Johns Hopkins University Press, Baltimore and London.

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