A cow moose and its calf run through the woods north of Moosehead Lake, as seen in this aerial photograph from January 2016. They were seen on a moose-collaring expedition with the Maine Department of Inland Fisheries & Wildlife Inland Fisheries. Gabe Souza/Staff file photo

Winter can be a time of hardship for wildlife. Ecologists call it a bottleneck, because food availability and nutrition are at their minimum, and can be a limiting factor to survival and population growth. Natural selection works overtime in the north to ensure the creatures that live here adapt to their environment. Large mammals like the moose are well suited to the deep snow and sometimes sub-zero temperatures, but even they face challenges.

Maine’s iconic moose represents a conservation success story as well as a cautionary tale. Around the turn of the 20th century, a nadir for many North American wildlife species, Maine’s moose population was estimated to be around 2,000 animals, the decline attributed to unrestricted hunting, clearing of forest land and increased incidence of brain worm. It was the dawn of the conservation movement, established and promoted mostly by hunters. Laws were established to protect moose and other species from excessive hunting, including a closed season on moose, beginning in 1936.

Populations slowly recovered, eventually to the point where the Maine Legislature re-established a moose hunt in 1980. After a year hiatus they passed a law setting the annual number of permits at 1,000, and limiting hunting largely to northern Maine. The moose population and hunting opportunities continued to grow. By the turn of this century, Maine’s moose herd reached a modern population peak, and was estimated at around 76,000 in 2012. All seemed well and while hunters, managers and wildlife watchers were delighted with the species’ recovery, Mother Nature had other ideas.

On a geologic time scale, the North American continent has continually undergone dramatic climatic changes. Four hundred million years ago Maine was at the bottom of the ocean. Ten thousand years ago it was under a mile-thick sheet of ice. Modern shifts we experience over a lifetime, or even since the dawn of man are mere fluctuations, and our most recent waver is negatively affecting moose. This mighty North Woods giant is being felled by the tiniest of woodland creatures.

Like all in its family, the winter tick relies on blood meals to complete its life cycle, and like many it is relatively host-specific, preferring to feed on large ungulates like elk, caribou and moose. One would think it nigh onto impossible that a tiny creature drawing a fraction of an ounce of blood from a massive moose could have any effect. They gain strength in numbers, attaching by the hundreds, thousands and even tens of thousands. This results in life-threatening blood loss, hair loss and behavioral changes.

The most affected are pregnant cows and calves, the latter of which may need to replace up to 60 percent of their blood supply. This results in poorer production and lower calf survival, and biologists believe that without intervention Maine’s moose population will likely destabilize. Fortunately, they’re working to implement adaptive methods to sustain our moose population.

The Maine Department of Inland Fisheries & Wildlife began a GPS collar study in 2014, where they have recorded infestations of up 40,000 to 60,000 ticks per moose. The next phase involves what they call an adaptive management study, wherein they will attempt to reduce moose population density within a particular study area (western half of zone 4) through increased hunting effort. The presumption is that lower (host) moose densities will lead to lower tick levels, and healthier moose. Time will tell. In the meantime, the moose and those who pursue them are left to endure another long Maine winter.

Bob Humphrey is a freelance writer and Registered Maine Guide who lives in Pownal. He can be reached at: bhunt@maine.rr.com