Vermont’s moose hunting season opens this weekend and for the first time fish and wildlife officials will count ticks on the animals brought into weigh stations.
They’re taking the step in light of tick-caused declines in moose numbers in New Hampshire.
Vermont’s moose population has fallen in recent years; from an estimated 5,000 animals in 2005 to about half that number today. Fish and Wildlife officials believe that’s largely due to their own efforts.
Most of the state’s moose population is in the Northeast Kingdom and biologists say at its peak it exceeded the carrying capacity of the habitat. Moose birth rates and body weights dropped as food sources were overtaxed.
The state responded by issuing more than one thousand hunting permits each year over a five year period, including permits requiring hunters to take only antlerless moose, in order to reduce the breeding stock.
“Eventually things started to look better. The weights started to go back up; the ovulation rates started to creep back up,” says wildlife biologist Cedric Alexander, the state’s moose project leader.
Alexander says moose numbers are now below target levels. The state would like to see the number of moose in the 3,000 – 5,000 range based on the available habitat and the cultural carrying capacity, which is an estimate of how many of the animals people are willing to tolerate in light of the risk of moose-auto collisions and other factors.
Alexander says there are opportunities for the herd to grow in areas outside of the Northeast Kingdom, were moose numbers are still relatively low.
While officials believe Vermont’s decline is due to the increased hunting, they’re also looking next door at New Hampshire, where there’s been a steep decline in moose numbers that is not linked to hunting. New Hampshire’s Executive Council has authorized a four-year study of the state's moose population, which involves attaching radio collars to track the moose population.
The main culprit in the Granite State’s decline is the winter tick. Unlike other species of tick, like deer ticks, these insects are active in the winter.
Alexander says in the fall the larval winter ticks mass in clumps on vegetation a few feet off the ground.
“If a moose walks by, the ticks on the end of the cluster grab on to it and they’re all grabbed on to each other so this huge glob of winter tick larvae, which are the size of a grain of sand come onto the moose and then they spread out. Moose usually have 30,000 to 100,000 ticks on them,”Alexander says.
The ticks weaken the moose by gorging on blood. The itching they cause results in loss of hair that makes moose more vulnerable to harsh weather.
Alexander says in the past 12 years, there have been two winters when ticks caused a higher mortality among Vermont moose, but it’s been nothing like New Hampshire.
The concern is that climate change and milder winters favor the tick population. The ticks drop off in April to begin reproducing. Alexander says by then they’re the size of grapes. If there’s snow on the ground it’s a less hospitable environment for them to survive; but the less snow there is, the better it is for the ticks.
Alexander says so far Vermont’s moose herd represents a success story: Fifty years ago, the state had no moose. But he says biologists will be studying the data they collect to see if there’s any cause for alarm.
In Minnesota, the moose die-off has been so severe that hunting season was canceled. There, officials blame brain and liver parasites. Alexander says historically those haven’t been a factor in moose mortality in Vermont.
