Moose populations: The thick and thin of it

Two different moose stories have made headlines in Minnesota in recent months.

One story tells of a long, ongoing moose decline in northern Minnesota. Since 2006, the state's moose population has plummeted by more than 55 percent, according to surveys by the Department of Natural Resources. State moose researchers say the odds of reversing the downward trend aren't good.

The other moose story is quite different. It tells of a moose population explosion. Surveys indicate the moose herd in question has been increasing by a whopping 19 percent a year. Plus, the survival rate of calf moose is extremely high, perhaps the highest ever recorded, researchers say.

Two moose stories; two different realities and … only 20 miles apart.

While Minnesota moose are slowly disappearing, the moose on Isle Royale National Park in Lake Superior — a mere 20 miles off Minnesota's North Shore — are approaching historic highs, according to 2016 surveys.

Hey, you can't make this stuff up.

So what is causing Minnesota's moose numbers to plummet while the island moose count soars?

DNR wildlife researchers have been seeking the answers to Minnesota's moose problems for decades. What is known is that Minnesota's moose are dying for a variety of reasons. Of more importance, is there anything to be done to eliminate or reduce these mortality factors to save Minnesota's moose?

It depends on who is asked.

If you asked many Minnesota deer hunters and others who spend time in the North Woods, the answer would be: "Get rid of some wolves."

DNR wildlife researchers typically scoff at such theories, correctly noting that moose and wolves have coexisted for a long time. Even as the state's moose count continued to decline, DNR officials were reluctant to even suggest that the high density of wolves in the state could be a leading moose problem.

In 2009, a state Moose Advisory Committee report — after reviewing a range of moose topics — came to the conclusion that stress from global warming may be the primary reason for the decline, along with other causes of mortality, such as winter ticks, poor nutrition (a habitat issue) and a parasitic brainworm (carried by whitetail deer). The 45-page report made no mention of wolf or bear predation.

In January 2016, DNR moose researchers announced they were on the brink of discovering what is killing Minnesota's moose. The suspects: poor health and increased predation. Using radio-collared moose, researchers investigated 47 moose fatalities and found that roughly 66 percent died of illnesses, such as brain worms, winter ticks, bacterial infections, liver flukes and severe malnutrition.

The other adult moose (33 percent) were killed by wolves, the DNR said, adding that one-third of the wolf kills possibly can be attributed to those moose already weakened by illnesses and vulnerable to wolf attacks. In a DNR study of moose calf mortalities, researchers tracking radio-collared moose calves found that 67 percent of them had been killed by wolves.

In a 2014 Star Tribune news story, renowned wolf researcher Dave Mech said he thinks wolves are playing a bigger role in the decline of northeast Minnesota moose than originally believed. He also discounted the idea that climate change was a major cause of moose mortality.

Nevertheless, DNR moose researchers last year contended that more study is needed, saying it could take another six years before the DNR had enough "data to determine long-term mortality trends and causes."

Meanwhile, the moose decline shows no signs of stopping.

Minnesota's moose population has plunged roughly 60 percent, from more than 8,000 animals in 2006 to fewer than 3,500 in 2015. Moose hunting was halted in 2013 by the DNR. Last fall, three Minnesota Chippewa Indian tribes, citing 1854 treaty rights, renewed their off-reservation hunting season for bull moose only.

So what explains the moose population explosion happening not far away on Isle Royale?

It's a much simpler story. It's the wolves. They're almost gone. At last count, two wolves remain on Isle Royale, down from an average of about 25.

This is a classic predator-prey plot to the extreme. For nearly a half century, moose and wolves have had a teeter-totter relationship documented by wildlife scientists on Isle Royale since 1958.

Rather than a so-called balance of nature, researchers found a dynamic tension: When the moose declined due to excessive wolf predation, eventually the wolves themselves declined for lack of moose meat; with fewer wolves hunting on the island, the moose population bounced back, after which wolves slowly increased as well. Such is the game of predator-prey.

Unfortunately, the predator-prey relationship on Isle Royale fell into disarray beginning in the 1980s when a disease, canine parvovirus, was inadvertently carried to the national park by visitors bringing their dogs. Unlike their domestic relatives, the island's wolves could not go to a vet to be vaccinated. They contracted the disease and simply died. Since 2009, the island's wolf population has dropped 90 percent. Today, only two remain.

As the wolf count went down, the moose count went up and up. How long will that continue? Nobody knows for sure, except that what goes up in nature typically must come down eventually, such as when moose eat themselves into winter starvation.

Can we compare the two moose stories? Is it fair? Yes and no. Moose in Minnesota and moose on Isle Royale lead similar lives in many ways. If climate change is a Minnesota moose problem, as the DNR suggests, one would assume the Isle Royale moose would suffer the same.

Winter tick outbreaks are known to kill Minnesota moose; however, the same tick outbreaks also occur on Isle Royale.

One big difference between the two moose populations is the presence of a brainworm disease that is carried by whitetail deer but is fatal to moose. The disease is prevalent in northern Minnesota and is a major killer of moose. On the contrary, Isle Royale moose are not affected because there are no deer on the island.

So how will the two moose stories end?

In recent weeks and months, a wolf rescue plan has been proposed on Isle Royale. Very simple. Introduce a new wolf population on the island to save and maintain the island's wolves (and the moose, for that matter).

Some argue that introducing wolves compromises the perfect wildlife laboratory, free of human interference, that once was Isle Royale. On the contrary, it's argued, the introduction of parvovirus to the island has already undermined that distinction. Like it or not, humans have had an impact on the island's ecological forces.

While we ponder helping the island's wolf population, a question: Why is there no similar campaign to restore Minnesota's moose population?

The Isle Royale experience clearly demonstrates that moose will thrive in the presence of reduced predation. While Minnesota's case is more complex, the state's moose are prey to a historically high wolf population. In one Minnesota wolf study area, the number of wolves roaming the north is the highest it's been in 40 years.

DNR researcher Glenn DelGiudice admitted, "Wolf predation is probably a little higher than we expected."

So is that part of the answer to Minnesota's moose mystery? Thin out a few wolf packs?

Please, no howling. For one thing, wolf control can't be done at the moment. Wolf management in Minnesota continues to be snarled in state politics and federal courts, where judges, not biologists, dictate wolf and moose relationships.

To protect moose from the spread of brainworm disease, the DNR has suggested thinning the deer herd in prime moose country. State deer hunters are cool to that idea, especially those who see more wolves than deer during the hunting season.

Consequently, Minnesota moose are caught in a political stalemate. Would DNR ever propose an intensive reduction in wolf packs roaming moose country? Highly unlikely.

Would state residents ever approve thinning wolves in the name of more moose? Highly unlikely. Wolf protectionists would go bananas, because for them the wolf is on a higher symbolic pedestal than moose.

Would state deer hunters make a sacrifice? To help moose avoid brainworm disease, would deer hunters support a drastic thinning of white-tailed deer in the state's primary moose range? Highly unlikely.

If Minnesotans refuse or are unable to assist a moose recovery, there's always a chance that nature will intervene.

Maybe the number of wolves will be decimated by natural forces, such as disease or winter starvation? Highly unlikely.

Maybe the moose somehow will increase their survival rate in the future? Highly unlikely.

Looking into the future, DNR researchers already have said it's doubtful if the northeast Minnesota moose herd will recover.

In the meantime, Minnesota's wolves thrive while Minnesota's moose do not. Twenty miles away on Isle Royale, the wolves have almost vanished while the moose overpopulate.

Two moose stories, both rather sad.

Ron Schara is a former Star Tribune outdoor columnist and host of "Minnesota Bound" on KARE-TV, Ch. 11.