ISLE ROYALE, MI - While there were many factors that played into Isle Royale’s once-robust wolf pack system collapsing to just two wolves in the space of a decade, a new study shows just how devastating inbreeding was to the big predators who lived on Michigan’s remote wilderness island.

As the wolves’ genetic pool got smaller, the physical deformities passed on through inbreeding got more noticeable: crooked spines, extra ribs and other genetic anomalies. These details and more are in a new report being released today and being published in the scientific journal Science Advances.

This study on what caused the island’s old pack system to crash is being announced at a time when the National Park Service is currently in the first year of an ambitious project to bring in more wolves to the Lake Superior island. They are needed to balance out a rapidly-expanding moose population. As of last fall, Isle Royale’s island-born wolves had dwindled to just two, while there were an estimated 2,000 moose.

There are now 14 wolves on Isle Royale. These include the older island-born pair - a father/daughter who researchers say cannot have viable offspring - and 12 other wolves that were trapped in Minnesota and Canada last fall and winter and released on the island. There have been two on-island wolf deaths as part of the project. A Minnesota male wolf was found dead last fall, and an Ontario male wolf was found dead recently, researchers reported today.

Knowing what led the old wolves’ multi-pack system to collapse in recent years is expected to help researchers as they go forward with their three-year plan to repopulate Isle Royale with predators.

It turns out, inbreeding was a big factor. It not only caused birth defects and other health issues for the wolves, but it made a tough life on a remote island even harder, researchers concluded.

"This new study, including whole-genome analysis of wolves from Isle Royale, directly links specific candidate genes with spinal abnormalities, which became more prevalent as decades progressed and inbreeding became more severe," said Rolf Peterson, research scientist in the School of Forest Resources and Environmental Science at Michigan Technological University.

The island’s first wolves are believed to have walked across an ice bridge to reach it in the 1940s, and the wolf population there hit an all-time high in the 1980s with about 50 wolves forming a handful of distinct packs.

The new study is really a genomics mapping project, looking at the last two island-born wolves, as well as studying wolf carcasses collected on the island over the years by Michigan Tech’s predator-prey team, which has been doing wolf/moose research on the island for more than 60 years.

Researchers used genetic samples from 11 Isle Royale wolves that were collected between 1988 and 2012. In that time window, there were up to 30 wolves roaming the island - a slow recovery from a disease that had nearly decimated the packs:

“In the early 1980s, the Isle Royale population crashed from an all-time high of 50 individuals to just 14 within a span of 2 years due to an outbreak of canine parvovirus. The population remained small until the mid-1990s, when it began to gradually increase. We found an overall trend ... consistent with high levels of inbreeding during this time of stagnant population growth.”

The gene pool got a big boost in 1997 when a new mainland wolf came over on an ice bridge and got very cozy with some of the island’s female wolves. But that diversity was short-lived, the study showed.

“In 1997, a male wolf naturally immigrated to Isle Royale and became a highly successful breeder. As shown previously, this event led to an immediate decrease in the mean level of inbreeding and an increase in heterozygosity in the population,” the study said.

“However, the migrant was so successful that his genome effectively swamped the population within ~2 generations and the level of inbreeding rapidly rose again.”

“This male wolf was such a successful breeder that within 2.5 generations, every individual in the Isle Royale population was related to him, leading to intense inbreeding among his descendants.”

Rib and spinal deformities seemed to be prevalent in this study of an inbred pack system. Researchers specifically looked at congenital vertebral anomalies, including the presence of extra vertebrae.

One example described in the study: “One wolf had three transitional vertebrae and an extra pair of ribs. This wolf was the product of a brother-sister mating and died while giving birth to a litter of pups thought to have been sired by her father. The pedigree-based inbreeding coefficient of this litter, in which all pups showed vertebral changes and all but one had extra ribs, was 0.375 (25). The pups died within hours, and our examination revealed that all eight had extra vertebrae and all but one had extra ribs.”

The last 2 island-born wolves on Isle Royale.

The only two island-born wolves left from Isle Royale’s old Chippewa Harbor Pack are this father-daughter pair. They had been the only wolves left on the island for several years until the new transplanted wolves began arriving last fall.

These two island-born wolves have a family tree whose DNA is too twisted to result in viable pups, researchers have said. They share the same mother, too, so they are also half-siblings. A pup they had in 2014 had a visibly deformed spine and died at about 9 months old, researchers estimate.

Still, the male, age 10, and the female, 8, remain “tightly bonded and highly territorial,” say researchers, who had good opportunity to study their movements in February and early March.

In concluding their new study, researchers determined the rapid collapse of genetic fitness within the Isle Royale wolf packs shows the big consequence of inbreeding when dealing with an isolated population.

“In the absence of recurring immigration, whether managed or not, the fate of a restored population on Isle Royale is grim. Nevertheless, wolf predation is an important top-down influence on Isle Royale, and its absence threatens the stability of the island ecosystem,” the study says.

"Active management of the population to reduce inbreeding may improve its long-term viability. We also recommend genomic screening of all wolves reintroduced to Isle Royale and their eventual descendants for the purposes of cataloging and monitoring ROH and deleterious alleles over time.

“The demise of the iconic Isle Royale wolf population provides lessons for its future restoration and guidance for the management of other species or populations to minimize the consequences of inbreeding.”

This genomics mapping project was led by a team from the University of California, Los Angeles, in collaboration with Michigan Tech, University of California, San Francisco and Swedish Museum of Natural History.