Isle Royale Wolf Population Drops to 3

The report of the 57th annual winter study of wolves and moose on Isle Royale, conducted from January to March 2015, is now available online.

Between January 2014 and January 2015, the population of wolves on the island decreased from 9 individuals to 3, pictured above, the lowest population since research began in 1959.  The three wolves are living in a single social group.  The gender and pack origin of these wolves is unknown.  One individual appears to be a nine-month-old pup and does not appear to be doing well.

It had been hoped that wolves from outside the island could move onto the island via an ice bridge which sometimes forms in the winter, connecting Isle Royale with nearby land in Minnesota or Canada.  On February 26, two wolves — one a radio collared female, one unknown — visited Isle Royale from the mainland, crossing the ice bridge.  The wolves did not stay long and did not interact with native wolves on the island.

Since 2009, the wolf population on Isle Royale has declined by nearly 90%.  Meanwhile, with predation on the island reduced, the moose population has grown at a mean rate of 22% per year.  During the most recent study, the moose population grew from 1050 to 1250.

Conservation scientists believe that predation (by wolves or other predators) is vital to the health of ecosystems inhabited by large herbivores like moose.  The National Park Service has stated that it had been considering genetic rescue of the wolf population (i.e., importing new individuals) as a means of mitigating this loss of predation on the moose population.  With only three known individuals on the island, “there is now a very good chance,” says the report, “that it is too late to conduct genetic rescue.”

The report also includes more information about Isabelle, the lone wolf who dispersed from the island in 2014 and was found shot dead on the mainland.

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