A 30-year ongoing study in Minnesota's Superior National Forest finds that nearly 70 percent of all gray wolf pups in the State die from a virus common in domestic dogs.A 30-year ongoing study in Minnesota's Superior National Forest finds that nearly 70 percent of all gray wolf pups in the State die from a virus common in domestic dogs.A 30-year ongoing study in Minnesota's Superior National Forest finds that nearly 70 percent of all gray wolf pups in the State die from a virus common in domestic dogs.