A remarkable story of how a single wolf changed the fate of an entire island's wildlife has been revealed by a long-term study of the Isle Royale National Park in Lake Superior, Michigan.
The study, published in the journal Science Advances, shows how the arrival of a lone wolf from Canada in 1997 boosted the genetic diversity and health of the island's wolf population, which in turn helped restore the balance of the forest ecosystem by controlling the moose population.
The Isle Royale wolf-moose project
THOMAS KIENZLE/AFP via Getty Images
The Isle Royale is a remote island that lies about 80 miles (130 kilometers) off the coast of Michigan and is home to a rich biodiversity of plants and animals.
Among them are two iconic species: wolves and moose, which have been the subject of the longest-running study of a predator-prey system in the world.
The Isle Royale wolf-moose project began in 1958 and has been conducted by generations of researchers from Michigan Technological University.
The project has documented the fluctuations of the wolf and moose populations over the decades, as well as their impacts on the forest vegetation and other wildlife.
The project has also revealed the challenges faced by both species due to environmental changes, such as disease outbreaks, climate variability, and genetic deterioration.
The Old Gray Guy
One of the most dramatic events in the history of the project was the arrival of a lone wolf from Canada in 1997.
The wolf, identified as M93 by researchers, but nicknamed "The Old Gray Guy" for his distinctive light-colored fur, crossed an ice bridge that briefly connected the island with the mainland during a harsh winter.
He was an immigrant in every sense of the word: he was unrelated to any of the existing wolves on the island, he was larger and stronger than them, and he had a different accent (his howls had a different pitch and duration).
The Old Gray Guy quickly became the dominant male in one of the island's three wolf packs and sired 34 pups over his lifetime.
His arrival was a boon for the island's wolf population, which had been suffering from severe inbreeding and low genetic diversity due to their isolation.
The inbreeding had caused lower reproductive success, higher mortality rates, and physical deformities among the wolves.
The Old Gray Guy introduced new genes that improved the health and vitality of his offspring and their descendants.
The Old Gray Guy's legacy did not stop at his own species. His presence also had cascading effects on the entire forest ecosystem, especially on the moose population.
Moose are the main prey of wolves on the island, and their numbers are influenced by both predation and food availability.
Moose feed on various plants, but their favorite are balsam firs, which are also important for providing habitat and food for other animals.
Before the Old Gray Guy's arrival, the moose population had been growing rapidly due to low predation pressure from the weakened wolf population.
This led to overgrazing of balsam firs and other plants, which reduced their growth and regeneration. The forest ecosystem was becoming degraded and simplified.
After the Old Gray Guy's arrival, however, things changed. His offspring and their descendants were more efficient hunters than their predecessors, and they increased their kill rate of moose.
This reduced the moose population and relieved some of the pressure on balsam firs and other plants. The forest ecosystem began to recover and diversify.
The lessons learned
The story of the Old Gray Guy illustrates how a single individual can have profound impacts on an entire ecosystem.
It also shows how genetic diversity is crucial for maintaining healthy populations and ecosystems.
Unfortunately, his positive effects did not last forever. After his death in 2006, his offspring became too numerous and interbred among themselves, leading to another decline in genetic diversity and health. By 2018, only two wolves remained on the island.
To prevent their extinction and restore their ecological role, park managers decided to intervene and relocate several wolves from Canada and the mainland US to the island between 2018 and 2020.
The new wolves have started to breed with each other and with the remaining native wolves, creating a new hybrid population that is hoped to be more resilient and adaptable to future challenges.
The Isle Royale wolf-moose project continues to monitor this experiment and provide valuable insights into wildlife conservation and management.
The project also inspires people to appreciate and care for nature's wonders. As Rolf Peterson, one of the lead researchers of the project said: "Isle Royale teaches us that all things are connected - even when it comes to an isolated island wilderness in Lake Superior".
