Speothos venaticus, the bush dog, is a small short-legged canid that inhabits the wet savannahs and forested areas of Panama, Colombia, Venezuela, the Guyanas, Brazil, Paraguay, northeastern Argentina, eastern Bolivia, and eastern Peru. Despite its wide range, the bush dog is scarce and may be threatened by loss of habitat. It is listed on CITES Appendix I and designated as vulnerable by the IUCN. Bush dogs are one of the most social canids, living in groups that may reach up to ten individuals. Preferred prey items are large rodents, including the capybara which is hunted cooperatively.

Two species of Speothos were present in South America during the late Pleistocene, S. venaticus and the now extinct S. pacivorus. The extinct species had a larger overall body size and a double-rooted second lower molar (m2). It has been proposed that Speothos originated in the Brazilian highlands sometime during the Pleistocene.

The paleobiogeography and evolutionary relationships of Speothos and other South American canids are unresolved. Morphological data suggest that Speothos is most closely related to another small canid, Atelocynus (small-eared zorro). The skulls of both Speothos and Atelocynus have short nasals that terminate rostral to the maxillary-frontal suture, a character shared with Vulpes (foxes). Speothos and Atelocynus also possess very small frontal sinuses that are minimally expanded. Recent analyses of molecular (mtDNA) data alone and in combination with morphological data support a sister-taxon relationship between Speothos and Chrysocyon (maned wolf); it has been suggested that these highly derived canids diverged at least 3 million years ago, invading South America as separate lineages.

Speothos is distinctive in that it shares similar hypercarnivorous modifications of the dentition with Cuon (dhole) and Lycaon (African wild dog). The crushing role of the post-carnassial molars is reduced. The lower carnassial (m1) of Speothos lacks the entoconid, creating a trenchant (cutting) heel on the tooth. The hypoconid on the heel (talonid) of the m1 fits into a basin in the M1 when the teeth are in occlusion. Speothos and Cuon exhibit reduction in both number and size of the post-carnassial molars.

This male specimen was obtained by M. Hildebrand on 29 September 1970 at Tarpon Zoo, Tarpon Springs, Florida. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning courtesy of Drs. Blaire Van Valkenburgh and Jessica Theodor of the Department of Organismic Biology, Ecology, and Evolution, University of California, Los Angeles. Funding for scanning was provided by Dr. Van Valkenburgh and by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin. This taxon is one of several canid carnivorans included in ongoing research of respiratory turbinates by Drs. Van Valkenburgh and Theodor.

The specimen was scanned by Matthew Colbert on 24 April 2001 along the coronal axis for a total of 453 slices, each slice 0.310 mm thick and with an interslice spacing of 0.310 mm. The dataset displayed was reduced for optimal Web delivery from the original, much higher resolution CT data.

Literature

Berta, A. 1984. The Pleistocene bush dog Speothos pacivorus (Canidae) from the Lagoa Santa Caves, Brazil. Journal of Mammalogy 65:549-559.

Berta, A. 1987. Origin, diversification, and zoogeography of the South American Canidae. Fieldiana Zoology 39:455-471.

de la Rosa, C. L., and C. C. Nocke. 2000. A guide to the carnivores of Central America. University of Texas Press, Austin. 244 pp.

Huxley, T. H. 1880. On the cranial and dental characters of the Canidae. Proceedings of the Zoological Society of London 16:238-288.

Kleiman, D. 1972. Social behavior of the maned wolf (Chrysocyon brachyurus) and bush dog (Speothos venaticus): A study in contrast. Journal of Mammalogy 53:791-806.

Langguth, A. 1975. Ecology and evolution in the South American canids; pp. 192-206 in M. W. Fox (ed.), The Wild Canids: Their Systematics, Behavioural Ecology and Evolution. Van Nostrand Reinhold Co., New York.

MacDonald, D. W. 1996. Social behaviour of captive bush dogs (Speothos venaticus). Journal of Zoology (London) 239:525-543.

Pollack, A., C. Holmes, T. Rowe, and B. Van Valkenburgh. 1998. Respiratory turbinals revealed by CT scans: a comparison of forest and savannah canids. American Zoologist 38(5):106A.

Tedford, R. H., B. E. Taylor, and X. Wang. 1995. Phylogeny of the Caninae (Carnivora: Canidae): The living taxa. American Museum Novitates 3146:1-37.

Van Valkenburgh, B. 1991. Iterative evolution of hypercarnivory in canids (Mammalia:Carnivora): Evolutionary interactions among sympatric predators. Paleobiology 17:340-362.

Van Valkenburgh, B., J. Theodor, A. Friscia, and T. Rowe. 2001. Respiratory turbinates of carnivorans revealed by CT scans: A quantitative comparison. Journal of Vertebrate Paleontology 21:110A.

Wayne, R. K., and S. J. O’Brien. 1987. Allozyme divergence within the Canidae. Systematic Zoology 36:339-355.

Wayne, R. K., E. Geffen, D. J. Girman, K. P. Koepfli, L. M. Lau, and C. R. Marshall. 1997. Molecular systematics of the Canidae. Systematic Biology 46:622-653.

Links
Speothos venaticus on The Animal Diversity Web (The University of Michigan Museum of Zoology)

Speothos venaticus on the IUCN Canid Specialist Group website

Facts and video on the bush dog from the BBC Online website

Photos of Speothos venaticus on the Animals of the Rainforest website

None available.