The raccoon dog (Nyctereutes procyonoides) is an enigmatic member of Canidae (Carnivora), the group consisting of dogs and foxes. The name Nyctereutes means “night seeking” (Ward and Wurster-Hill, 1990), and although the species is thought to be nocturnal typically, raccoon dogs are quite active during daylight hours (Ward and Wurster-Hill, 1989).

Raccoon dogs are characterized generally by yellow-brown fur and black masking around the eyes, reminiscent of a raccoon. Fur along the shoulders, back, and tail is tipped with black. The snout of Nyctereutes is shortened in relation to other canids, and this leads to identification and systematic problems. They were closely allied with Procyonidae (raccoons) in the past, but morphological features of the skull suggest that Nyctereutes does in fact belong in Canidae. Even so, remains of Nyctereutes are often confused with those of Meles (Mustelidae) in Asian archaeological sites (Hidaka et al., 1998).

Nyctereutes is unique among canids in that it hibernates and undergoes a four- or five-month-long winter sleep from November to March (Ward and Wurster-Hill, 1990). During the winter sleep, metabolism can decrease by 25%, and the species can maintain a constant protein catabolism for at least 60 days (Mustonen et al., 2004). Raccoon dogs have been known to increase food uptake immediately before hibernation, and some may even forage during winter months.

Additional diagnostic characters include a slight interparietal crest, a distinct rounded subangular lobe on the posterior margin of the mandible, reduced carnassial blades, and a dental formula of I3/3, C1/1, P4/4, M2/3 (Nowak, 1991; Ward and Wurster-Hill, 1990). The average mass of an adult raccoon dog is 4-5 kg, and height at the shoulder is around 380 mm. The tail contributes less than 30% of the body length (Ward and Wurster-Hill, 1990).

Although Nyctereutes is monospecific today, the genus was more diverse in the past. At least six fossil species have been recovered from deposits ranging in age from mid Pliocene to late Pleistocene in Europe and Asia. The original distribution of Nyctereutes procyonides was in eastern Asia, although the species was introduced into Europe and western Asia during the second quarter of the 20th Century for the fur industry (Ward and Wurster-Hill, 1990). The range of raccoon dogs has even extended as far west as Great Britain (Nowak, 1991).

Nyctereutes inhabits areas of forested streams, river valleys, and lakes where underbrush can provide adequate cover. Raccoon dogs are excellent fishers and their diet consists mainly of fish and amphibians. They will also consume other small vertebrates, invertebrates, berries and garbage (Ward and Wurster-Hill, 1990). They live in pairs or in small groups, and are not greatly disturbed by human activity.

Additional Information on the Skull

Click on the thumbnails below for labeled images of the male skull in standard anatomical views.

Dorsal view	Lateral view	Ventral view

This specimen, a female, was collected from Suifu, Sichuan, China in 1929 by D. C. Graham. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning courtesy of Dr. Blaire Van Valkenburgh of the Department of Ecology and Evolutionary Biology, University of California, Los Angeles. Funding for scanning and image processing 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. The raccoon dog is one of several canid carnivorans included in ongoing research of respiratory turbinates by Dr. Van Valkenburgh.

Lateral view of specimen	Dorsal view of specimen	Ventral view of specimen

The specimen was scanned by Matthew Colbert on 15 December 2005 along the coronal axis for a total of 780 slices. Each slice is 0.15 mm thick, with an interslice spacing of 0.15 mm and a field of reconstruction of 71 mm.

Literature

Hidaka, S., M. Matsumoto, H. Hiji, S. Ohsako, and H. Nishinakagawa. 1998. Morphology and morphometry of skulls of raccoon dogs, Nycetereutes procyonoides and badgers, Meles meles. Journal of Veterinary Medicine Science 60:161-167.

Mustonen, A. –M., P. Nieminen, M. Puukka, J. Asikainen, S. Saarela, S. –L. Karonen, J. V. K. Kukkonen, and H. Hyvärinen. 2004. Physiological adaptations of the raccoon dog (Nyctereutes procyonoides) to seasonal fasting-fat and nitrogen metabolism and influence of continuous melatonin treatment. Journal of Comparative Physiology B 174:1-12.

Nowak, R. M. 1991. Walker’s Mammals of the World. Fifth Edition, Volume II. The Johns Hopkins University Press, Baltimore, MD. 1629 pp.

Ward, O. G. and D. H. Wurster-Hill. 1989. Ecological studies of Japanese raccoon dogs, Nyctereutes procyonoides viverrinus. Journal of Mammalogy 70:330-334.

Ward, O. G. and D. H. Wurster-Hill. 1990. Nyctereutes procyonoides. Mammalian Species 358:1-5.

Links

Nyctereutes procyonoides page on the Animal Diversity Web (University of Michigan Museum of Zoology)

N. procyonoides page on the Lioncrusher's Domain

N. procyonoides page on Canids.org

Front page image.