Please read the following scenario to understand Michigan's Isle Royale, located in Lake Superior. In the winter of 1949, a pair of wolves crossed the ice from Canada to the island. When the wolves arrived, the moose population, which had no predators, was large. However, in 1982, the wolf population suddenly decreased. The problem was a disease brought by the wolves. This pattern continued until 1978 and spread rapidly in about six months. Infected animals can survive for a few days. It is hypothesized that the virus arrived on the island carried on the shoe of a human traveler. The wolf population decreased from 50 to 14 individuals in a year, while the moose population increased. However, in 1996, the moose population experienced a major crash due to a harsh winter. More than 500 animals died. The virus introduced to the island in 1982 that reduced the wolf population is an example of a density-dependent factor.