The wolf effect after the butterfly effect? By crossing an ice bridge linking Canada to an isolated island in the northern United States, a lone wolf eventually regenerated the endangered local pack but also an entire island ecosystem, American researchers conclude after years of research.
“This is the first study to show that genetic issues don’t just impact a given population and increase the risk of that population becoming extinct, but also have broad implications for all species,” explains Sarah Hoy, lead author of this study published Wednesday, August 23 in the journal Science Advances.
The team of this ecology researcher at the Michigan Technological University scrutinized the ecosystem of Isle Royale, located on the American side of Lake Superior, a vast expanse of fresh water wedged between Canada and the United States. States, after the arrival on site of a lone wolf unknown to the local pack.
It was in 1997 that this newcomer, baptized “M93” in the context of the study but more affectionately “the old gray wolf” by the researchers, crossed an ice bridge between Canada and the island. The first known wolves arrived in this territory in the 1940s and they mainly hunted elk. But in the 1980s, the introduction of a virus, the “canine parvovirus”, into this ecosystem contributed to decimating the local population of wolves, which fell from around fifty individuals to a dozen.
Height gain, moose and spruces
The arrival of the old gray wolf changes everything. Being particularly imposing, a key advantage against the elk, quickly becomes the new “breeding male” among one of the three packs on the island, to the point of being the parent of 34 cubs. As a result, not only is the gene pool of the island’s wolves diversifying, but their ability to kill moose improves as they grow in size.
The reduction in the number of elk, herbivores eating up to 14 kilos of vegetation per day, subsequently leads to a transformation of the ecosystem. Balsam fir trees began to grow again at a rate not seen in decades, which was vital for the forest and therefore a myriad of plants and species, the US researchers conclude.
But the story doesn’t end there, and the wolf population boom eventually contributed to a new imbalance in Isle Royale’s ecosystem. After the death of “M93”, who had given his genetic heritage to about 60% of the wolves, the population began to decline again – due to inbreeding – to the point where there were only two wolves left: a father and his daughter, who was also a half-sibling.
A reintroduction program for the species launched five years ago has, however, restored a better balance in this isolated ecosystem where around thirty wolves now live and just under a thousand elk, also known as “moose”. in North America.
For Sarah Hoy, the author of the study, the case of the old gray wolf could undoubtedly apply to other populations of inbred predators in danger of extinction such as cheetahs by showing that the introduction of one or a few individuals in a gene pool not only renews a population but also an ecosystem.
Professor of ecology at Oregon State University, William Ripple qualifies the work of his colleague from Michigan, in which he did not participate, as “important”, showing that “genetic processes can limit the ecological impacts’ of a given species.
2023-08-24 11:09:19
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