According to the Minnesota Climatology Office, the earliest recorded trace of snow in the Northeast region of Minnesota was on Aug. 31, 1949, which served as a harbinger for the 170 inches of snow that would accumulate during the 1949- 1950 winter season – the most recorded in Minnesota in one season. It was also the highest recorded snowpack as of March 28, 1950 at 75 inches (coincidentally, my height).
It was during this severe winter that Isle Royale lost half its moose population.
Nearly half-a-century later, another severe winter would decimate Isle Royale’s moose population. A significant contributing factor, however, was the introduction of canine parvovirus in 1980, when a visitor brought his pet dog to the wilderness area.
The newly introduced contagious disease, which does not infect humans, killed off half the wolf population. That allowed the moose population to grow out of control, destroying the food supply on the island. So much so that two-thirds of the island’s moose population – which had approached 2,500 – died of hunger during the bitter winter of 1996. A winter that experienced temperatures plummeting to -57º F in, aptly named, Embarrass, Minnesota. A winter that followed on the heels of 1994 winter storms that witnessed 47 inches of snow in a single storm in neighboring Lake County. The moose and white-tailed deer populations in the Boundary Waters also took a hit, with severe winter losses in 1995 and 1996.
Weather can have a significant influence on moose numbers; how be it, it is a lot more nuanced than simply weather, as noted above. The complex interactions of weather, prey, predators, competitors and parasites all alter the long-term survival of moose populations. As mentioned in a previous column, certainly the “winter tick” plays a convincing role in determining whether infested moose will subsist through winter.
Since they were first introduced in the late 1800s, moose numbers in Newfoundland have shown a steady growth from just a few animals to an estimated 120,000. I asked Newfoundland’s Big Game Senior Wildlife Biologist, Paul Saunders, if he was aware of any collapse in the moose population due to severe weather? He referenced 1995, as well, as being a particularly hard winter on moose in Newfoundland. “We had a real lot of snow accumulation that primarily impacted moose calves as they were unable to move in the deep snow, which amounted to approximately 2 meters (6.5 feet). Calves couldn’t get to forage and, unfortunately, died of starvation.”
Research biologists Lyle A. Renecker and Charles C. Schwartz noted, “The long legs of moose serve them well when traveling in deep snow. Moose have small hooves in combination with legs nearly twice as long as those of white-tailed deer, yet comparable ‘loading’ (i.e., distribution of weight per step). Consequently, moose are much more capable of enduring deep snow to find and reach available browse. Under soft snow conditions, snow accumulation of 2 feet or less does not inhibit moose from the standpoints of mobility or energetics. However, they are more often constrained by compacted or crusted snow conditions than are other species. Compaction or crusting of snow at almost any depth places an extreme energetic limitation on moose, beside dramatically reducing their foraging range.”
Renecker and Schwartz referenced a 4-inch balsam fir near Grand Marais that was browsed by moose to a height of 10 feet during winter when the snowpack was so deep the animals could not crater to understory, reach overstory of birch and aspen or move for an extended period to a better foraging area.
Another inherent problem with deep snow accumulation is that it can heighten the vulnerability of moose to predation. Wolves researcher L. David Mech and others suggest deep snows during consecutive winters create a cumulative impact on the physical condition of moose, which predisposes them to predation.
Winter can be a time of great natural stress on moose (they aren’t the only ones), and even if the moose are not dispatched by packs of wolves the added stress of being harassed and stalked repeatedly will cause moose to use up energy they should be reserving to “weather” winter.
Darrin McGrath – Newfoundland author of the book I paid more than a few loonies for while in Newfoundland – writes, “When snow is deep with hard crust, moose are easy prey for wolves. The moose breaks through the hard crust and flounders in the deep snow as it tries to flee, exhausting itself. The crust will carry the weight of the dog predators that tear at the terrified moose. Since the moose may be up to its belly in snow, it loses its most effective defense: kicking or flailing with its legs. In many cases, the moose is devoured alive.”
Healthy adult moose will often stand their ground when confronted by a wolf pack, while younger inexperienced moose run and are killed. “It is important for moose to use their mother’s defensive behavior,” say wildlife biologists Warren Ballard and Victor Van Ballenberghe, referring to charging and kicking at the predators. But in deep snow it becomes near impossible for a moose to raise its legs and kick at swarming dogs of any type.
Biologist Rolf Peterson witnessed declines in the moose population on Isle Royale in the 1970s, when calves and young adult moose became vulnerable to wolf predation because of severe winters. Moose numbers declined from roughly 1,200 to 600.
Mature bull moose, on the other hand, will often become solitary in winter to avoid excessive energy allocation to social interaction. Optimal strategy is to maintain a more solitary lifestyle, reduce activity levels, decrease travel distances, increase bite size and inhabit an area of high food availability (are we talking moose here, or a few guys I’ve met over the years?).
What about summer? How do moose manage day-to-day living in the context of thermo-regulation – keeping their “cool,” given the fact they don’t sweat. I’ll tackle heat in next week’s epilogue.
Observation: “To conserve the moose resource for the future many management decisions will be made with political overtones, but they must be formulated with a basic understanding of the fundamentals of moose biology and the accompanying management constraints. Moose management is and will remain social and political as well as biological.” (Albert W. Franzmann and Charles C. Schwartz) Next week: Moose Management—Epilogue
Former Cook County Commissioner Garry Gamble is writing this ongoing column about the various ways government works.
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