Distemper in Yellowstone wolf pups
by Yellowstone National Park
September 18, 2009
Since wolves were reintroduced in Yellowstone in the 1990s, there have been three years when the pup survival rate was extremely low: 1999, 2005, and 2008.
Canine parvovirus was believed to be the cause of the wolf pup deaths in 1999 and 2005. That was because parvovirus is known to cause a high mortality rate in domestic dogs, and was suspected in the high death rate of wolves at Isle Royale National Park in Michigan in the early 1980s.
Results of newly published research point to canine distemper as the cause of the low pup survival rates.
Researchers took blood samples from wolves and coyotes in Yellowstone National Park. They looked for exposure to a number of canine diseases. The results indicate that some diseases like parvovirus are chronic in the park’s wild canines.
However, signs of distemper appeared only in the years when pup mortality was high. Since distemper weakens the immune system and makes infected animals susceptible to other infections, it can be difficult to determine the actual cause of death.
The research also indicates that the wolf population seems to fare well despite some chronic infections, and rebounds well from periodic exposure to distemper.
While the research was unable to conclusively determine the episodic source of the canine distemper, data suggests it is not linked to the region’s domestic dog population.
The research was conducted by the Yellowstone Wolf Project, the University of Minnesota, and the Yellowstone Ecological Research Center.
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