In 1997, a lone wolf crossed an ice bridge that briefly connected Canada with the lonely Isle Royale, located in Lake Superior off the coast of Michigan and known for its rich biodiversity. His arrival restored the sagging fortunes of the larger wolf population, plagued by disease and inbreeding. It caused cascade effects that boosted the overall health of the forest environment, according to a study published Wednesday in Science Advances.
“Issues like inbreeding and low genetic diversity are an important concern for scientists,” first author Sarah Hoy, an ecologist at Michigan Technological University, told AFP. “But this is the first study that shows when you have these genetic issues, they don’t just impact the particular population and increase the risk that they will go extinct: they also have these really big knock-on effects on all the other species.”
The first wolves arrived on the island in the late 1940s
The first wolves arrived on the island in the late 1940s, and their principal food is moose, giving rise to the world’s longest-running study of a predator-prey system. However, by the 1980s, the wolves were in jeopardy due to the introduction of canine parvovirus, which reduced their population from 50 to roughly 12. Though the virus was eventually eradicated, the population did not recover immediately. The cause was significant inbreeding, which resulted in lower reproductive success as well as inferior health outcomes such as spine abnormalities, which are common in purebred dogs.
“If you’re a wild wolf and you’re having to take down prey like a moose that’s eight times your size, that can make life in the wild really tough for you,” Hoy said. Enter the immigrant, identified as “M93” by scientists, but affectionately nicknamed “The Old Gray Guy.” M93 was unrelated to the existing population and also had the advantage of being unusually large, — a big benefit when defending turf from rivals or taking down 800-pound ungulates. Ambien
He swiftly rose to the position of breeding male in one of the island’s three wolf packs, siring 34 puppies and significantly boosting the genetic health of the population as well as the kill rate of its prey. Moose are avid herbivores that can eat up to 30 pounds (14 kilograms) of grass per day. By diminishing their numbers, wolves helped restore equilibrium to the forest, most notably in the impacts on balsam firs, a species often utilized as Christmas trees.
By 2008, two years after his death, M93 had inherited 60% of the wolf population’s gene pool
With fewer moose, the trees began to grow at rates not seen in decades, which is critical for the regeneration of the forest and the numerous plant and animal species that rely on it. M93’s entrance offered about a decade of benefits before the situation deteriorated again, paradoxically as a result of his extraordinary reproductive success.
By 2008, two years after his death, M93 had inherited 60% of the wolf population’s gene pool, resulting in a resurgence of genetic degeneration. After his mate died, M93 began breeding with his daughter, and subsequent inbreeding by other members drove a rapid population reduction until 2015 when there were only two wolves left: a father-daughter pair who were also half-siblings.
Fortunately, a restoration initiative that began in 2018 has restored balance to the system, and there are now approximately 30 wolves and just under a thousand moose on the island. A major takeaway for Hoy is that the same idea of transplanting only a limited number of animals may be applied to other threatened predator species, such as lions or cheetahs, to better their ecosystems.
According to William Ripple, an ecology professor at Oregon State University who was not involved in the study, it is an “important study” that increases understanding “by showing that genetic processes may limit the ecological effects of a keystone species, the gray wolf.”