North American male wolf M93 sired 34 pups, helping to improve the genetic health of the wolf population on Isle Royale and increase hunting success rates.
Wolf M93 (the larger, lighter-colored male stands in the foreground, near center) and his littermates. Photo: John Vucetich/Michigan Technological University/AFP
In 1997, a lone 'immigrant' wolf crossed the ice bridge connecting Canada to Isle Royale in Lake Superior in North America. Its arrival helped restore the island's wolf population, which had been weakened by disease and inbreeding, and improved the health of the forest ecosystem, according to a study published in the journal Science Advances on August 23.
"Problems like inbreeding and low genetic diversity are big concerns for scientists. But this is the first study to show that these genetic problems don't just affect a particular population and increase the risk of extinction, but also have a major impact on all species," said Sarah Hoy, an ecologist at Michigan Technological University and a member of the research team.
The first wolves arrived on Isle Royale in the late 1940s, and their main prey was moose. By the 1980s, the introduction of canine parvovirus reduced the wolf population from 50 to about 12. The disease later disappeared, but the wolf population did not recover immediately. The cause was inbreeding, leading to low reproductive success and poor health.
M93 was unrelated to the island’s old wolf population. He was also unusually large—a huge advantage when defending territory or taking down moose that weighed up to 400kg. M93 quickly became the primary breeding male of one of the island’s three wolf packs. He sired 34 pups, greatly improving the population’s genetic health and kill success rate.
Moose are voracious herbivores, consuming up to 14 kg of vegetation per day. By reducing the moose population, wolves help restore balance to the forest, especially the Abies balsamea fir tree. The reduction in moose numbers has allowed the tree to grow at a rate not seen in decades. This is important for forest regeneration as well as for the countless species of plants and animals that depend on the forest.
The benefits of M93’s presence lasted for about a decade. Then, the situation deteriorated again due to its strong reproductive capacity. In 2008, two years after M93 died, 60% of the wolf population’s gene pool had been inherited from M93, causing a return to genetic decline. By 2015, there were only two wolves left in the population. They were a father-daughter pair, who were also half-siblings.
A restoration program that began in 2018 has brought balance back. The island now has about 30 wolves and nearly 1,000 moose.
For Hoy, the remarkable point is that adding just a small number of individuals could be applied to other endangered carnivore populations that are suffering from inbreeding, such as lions or cheetahs, to restore ecosystems in a similar way. William Ripple, an ecology professor at Oregon State University, said the study was important, showing that genetic processes can limit the ecological impact of a keystone species like the gray wolf.
Thu Thao (According to AFP )
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