isle royale

A foggy morning face off! Two young bull moose test each other at Isle Royale National Park in Michigan. This photo was taken in Tobin Harbor as the moose locked horns. Photo by Carl TerHaar (

Isle Royale wolf population drops to 3

Arpil 18th - 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.


Meet Old Gray Guy, the wolf who saved Isle Royale. 

In 1949, a pair of wolves wandered across an ice bridge made to the Isle Royale, during a harsh winter from Ontario. Since that winter, the wolves that live on Lake Superior’s Isle Royale are completely isolated from all other wolves. Inbreeding was becoming a serious threat for the wolf population.

But in 1997, one immigrant male wolf injected some much-needed fresh genes into the mix, and we know because of the poop he left behind. The arrival of this extremely virile wolf may go a long way to keep the population genetically viable.

The Old Gray Guy (so-named because as he aged his fur became very pale, an unusual phenomenon) was larger and more territorial than most of the native wolves. His own pack grew to an unusually large 10 wolves, and displaced and drove to extinction one of the other 4 packs on Isle Royale. It was determined that by 2009, 56% of the wolves on Isle Royale had descended from Old Gray Guy. By the end of his eight years of breeding, he produced 34 pups.

Scientists expected that this would create a “genetic rescue” population boom, but it did not happen. The average reproduction after the Old Gray Guy arrived was no different from before. Yet this does not mean that he had no effect. What excites researchers about the Old Gray Guy is that he may have performed genetic rescue, which involves the sudden influx of new genes into an otherwise stale population. Isolated populations risk losing genetic diversity, which in turn makes them far more vulnerable to being totally wiped out by disease.

Sadly, the genetic rescue may have come too late for the Isle Royale wolves. While there were once three packs, now there’s only 8 wolves left, who suffer inbreeding problems, and right now it’s most likely their population will die off.

Read more on the current status of wolves on Isle Royale here.

(Old Gray Guy is the lighter coloured wolf in the middle of the picture)