A timeline of the wolf and moose populations on Isle Royale since 1959

A center-piece of the wolf-moose research is having watched wolves and moose abundance fluctuate over the past six and a half decades. Those fluctuations are an epic story all to themselves.

Graph 1 (5 years): After observing relatively constant abundances for five years, it seemed that the wolves and moose of Isle Royale were bound to some balance of nature.

Graph 1 (5 years): After observing relatively constant abundances for five years, it seemed that the wolves and moose of Isle Royale were bound to some balance of nature.

Graph 2 (14 years): Over time wolf abundance fluctuated a bit. But, after a series of mild winters moose abundance doubled. There’d been a major shift in the balance.

Graph 2 (14 years): Over time wolf abundance fluctuated a bit. But, after a series of mild winters moose abundance doubled. There’d been a major shift in the balance.

Graph 3 (22 years): Then a series of severe winters, increased wolf predation, and moose abundance was cut in half. The wolf population soared to 50 individuals.

Graph 3 (22 years): Then a series of severe winters, increased wolf predation, and moose abundance was cut in half. The wolf population soared to 50 individuals.

Graph 4 (2 years later): Humans inadvertently introduce canine parvovirus, a wolf disease. The wolf population crashes.

Graph 4 (2 years later): Humans inadvertently introduce canine parvovirus, a wolf disease. The wolf population crashes.

Graph 5 (after 38 years): Wolves made a partial, short-lived recovery. Then they fell even lower, with abundances spending the better part of a decade in the low teens. During that same period moose abundance soared.

Graph 5 (after 38 years): Wolves made a partial, short-lived recovery. Then they fell even lower, with abundances spending the better part of a decade in the low teens. During that same period moose abundance soared.

Graph 6 (the following year): Intense competition for declining forage, an outbreak of winter ticks, and a severe winter. They all conspired against the moose population, which collapsed in 1996.

Graph 6 (the following year): Intense competition for declining forage, an outbreak of winter ticks, and a severe winter. They all conspired against the moose population, which collapsed in 1996.

Graph 7 (a decade later): Moose continue to dwindle. In 1997, a wolf emigrates from Canada, bringing an infusion of new genes. In response, wolf abundance increases, albeit erratically.

Graph 7 (a decade later): Moose continue to dwindle. In 1997, a wolf emigrates from Canada, bringing an infusion of new genes. In response, wolf abundance increases, albeit erratically.

Graph 8 (after 60 years): The wolf population’s genetic rejuvenation only lasted about a decade. Inbreeding depression returns. The wolf population reverses course and nearly goes extinct. Freed from wolf predation, the moose population soars to th

Graph 8 (after 60 years): The wolf population’s genetic rejuvenation only lasted about a decade. Inbreeding depression returns. The wolf population reverses course and nearly goes extinct. Freed from wolf predation, the moose population soars to the point of severely impacting forest growth, upon which the moose depend for food.

Graph 9 (after 66 years): The National Park Service decides to restore wolf predation by bringing wolves to Isle Royale in 2018 and 2019. The effort is successful and wolf abundance returns to typical levels within a few years.

Graph 9 (after 66 years): The National Park Service decides to restore wolf predation by bringing wolves to Isle Royale in 2018 and 2019. The effort is successful and wolf abundance returns to typical levels within a few years.

Graph 10 (after 66 years): Moose abundance declines, at first due to lack of food. Then the decline in moose abundance continues, now fueled by higher levels of predation.

Graph 10 (after 66 years): Moose abundance declines, at first due to lack of food. Then the decline in moose abundance continues, now fueled by higher levels of predation.