Can Vermont’s Moose Population Take the Heat?

A friend of mine was walking along a secluded trail earlier this year when he came across a sad sight – a small, dead moose calf. The alarming part of this image was the moose’s apparent cause of death; the moose was covered in thousands of engorged ticks.

Everyone knows that it is a bad year for ticks, but these particular ticks are thriving and that is due to climate change. Winter ticks are one of a moose population’s greatest threats. They latch on to the moose and start draining the moose of its blood. This can greatly weaken and irritate the moose, and there is no easy way for the moose to rid itself of these pests. Their best bet is to rub against trees and try to scrape them off, but the moose often removes some of its precious insulating fur in the process.

This fur keeps the moose cool in the summer and warm in the winter. Their fur combined with their thick skin has allowed them to adapt to colder environments, not warm ones. If moose are subject to temperatures warmer than they can handle, they start to experience “heat stress.”

To fight off heat stress, a moose will have to cool off quickly. They do this by finding shady areas, finding cool water to soak in, or finding a windy place to lie down. However, if a moose is trying to stay cool, then it can’t spend valuable time foraging. If a moose spends all of its time trying to stay cool instead of foraging for winter, then it won’t have the strength to survive the harsh, cold months.

Not only is winter a concern, but if a cow (mature female moose) is not the proper weight, her offspring will also be undersized and disadvantaged from the start — assuming she can even carry a calf. Sometimes cows are so malnourished that they can’t reproduce, further limiting the moose population.

Moose start to experience “heat stress” at temperatures above 57°F in the summer and above 23°F in the winter. Heat stress also makes moose more vulnerable to winter ticks.

Unfortunately, the average temperature in Vermont during the summer 65°F is and during the winter is 19°F. As you can see, Vermont’s moose population is already outside this range due to the warmth here. With temperatures expected to rise on average by 9-13°F in the next 100 years, who knows if Vermont’s moose population will survive?

Climate change is causing shorter, warmer winters, which negatively impact moose in two significant ways.

First, shorter winters allow for a larger number of winter ticks to reproduce. Vermont is managing the moose and deer population (white tail deer being the primary host), but that management might not matter if winters keep getting easier for the ticks.

Secondly, climate change is affecting trees in the forest. Moose rely on shade from spruce, fir, and hemlock trees to keep cool in the summer and to provide cover in the winter. Climate change causes these species to be replaced by oak and hickory which do not provide the same benefits for the moose. These trees will still provide food and a surface for them to endlessly rub against until they strip themselves of their fur due to the ticks, but it will not provide them with the vital cover that they need.

Overall, the state of Vermont is doing a good job managing some of the symptoms of climate change. By keeping the winter tick population down, they are giving moose a fighting chance at sustaining a viable population in the area. However, it will take a collective effort by us all, not just the State, to tackle the underlying cause of a dying moose population in Vermont; climate change.


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