CHAMPAIGN, Ill. -- Gray wolves roaming wild along Alaska's Yukon River have bigger hearts than their zoo-bound cousins in Minnesota, and some of the wild wolves carry an enzyme previously found only in dogs -- which raises questions about their overall health, researchers say.
These factors could be important components of a long-sought biological equation that defines normal health parameters of animal populations, said Peter Constable, a researcher in the University of Illinois College of Veterinary Medicine. The enzyme's presence also strengthens the domestic dog's theorized evolutionary link to gray wolves (Canis lupus), he said.
The enzyme discovery was published in the Journal of Zoo and Wildlife Medicine. The heart comparison was reported in Comparative Biochemistry and Physiology. The companion studies looked at wolves that have lived sedentary lifestyles in captivity for two or more years in Minnesota and 11 free-ranging wolves in east central Alaska. The Alaskan wolves traveled an average of some 40 miles daily, including one overnight roam of 80 miles, during the observation-and-capture period.
"When you compare animals in zoos and wild populations to diagnose disease or prove their health, a biologist has to do certain things such as physical exams and blood tests," Constable said. "Then you have to compare their findings to a normal population. The real dilemma is, what is normal?" Is it the zoo population or a wild population? Which values are accurate?"
Three of the 11 wild wolves carried the slow-developing liver enzyme called corticosteroid-induced alkaline phosphatase, which U. of I. scientist Walter E. Hoffman previously had discovered in dogs and was believed to be unique to them. None of the captive wolves had the enzyme, which reflects long-term stress and indicates the presence of hepatic disease. Other U. of I. researchers, including doctoral student Charles E. Wiedmeyer, are studying the molecular qualities and mechanisms of the enzyme.
"In all likelihood, the three wild wolves carrying the enzyme are not healthy," Constable said. "If you are thinking of moving one of these enzyme-carrying dogs into another area to rebuild or reintroduce a population, it probably would not be a good idea."
Electrocardiograph exams on the populations revealed that the wild wolves had substantially larger hearts -- up to 2-1/2 times the size -- of those found in Minnesota's zoo wolves. Such differences were much larger than those reported between Alaskan sled dogs and inactive dogs, as well as those found between elite human endurance athletes and less active individuals.
Constable's team included Ken Hinchcliff of Ohio State University's department of veterinary clinical sciences. An Ohio State zoo-research program funded the work.