A Telltale Tick: Scientists Gauge Tick Impact On Moose Population
Hunters took 169 moose during Vermont’s 2014 archery and rifle seasons, according to state Fish and Wildlife officials.
After taking a moose, hunters are required to check in at one of the big game reporting stations around the state so biologists can document information that will help them better understand the population. That information also helps the Fish and Wildlife department determine how many moose permits to award the following year.
About halfway through rifle season, on a cold and drizzly afternoon, wildlife biolgist Jane Lazorchack was checking in her sixth moose of the day at the town garage in Middlesex.
Jim Jewell from Monkton, Vermont, pulled in under the tin roof. A large female moose was stretched out in the trailer attached to his truck. Jewell and five other hunters used a horse to drag this moose out of the woods near Spruce Lodge in Lincoln.
Lazorchak took Jewell’s tag and permit and marked the numbers down on a sheet of paper. She asked the hunters a lot of questions— rifle? (Yes.) What gauge? (.270) Was she lactating? (No.) Did they collect the ovaries? (They weren't sure, but they had a plastic bag of "something.")
Collecting the ovaries is a requirement. They're sent off to scientists who use them to analyze how many calves the moose has given birth to. The herd's reproductive rate has been in decline in Vermont for a number of years. Fish and Wildlife officials had initially responded by increasing the number of hunting permits.
“The theory was that the habitat isn’t very good anymore," said Lazorchak, "so they brought down the number of moose thinking that, over time, if you brought the population down, the reproductive rate would come back up."
At the end of moose season this year, the average tick count was about 16-- quite a drop from last year, when the average count was above 27.
But the rate hasn't bounced back and biologists aren't sure why.
That's just one of the worries on the minds of Vermont biologists, who are concerned that the moose herd is not as robust as it should be. In some parts of the country, including Vermont, ticks are blamed for the deaths of many moose. So Fish and Wildlife staffers are counting ticks on every moose brought in to the reporting station.
Lazorchak explains that they can't take the time to count every possible tick on these large animals, so they take a sample and extrapolate.
“We’re going to look at the animal in four spots—take four samples on the neck, the shoulder, the rib and the rump.”
Lazorchak examines the moose hair in 10-centimeter quadrants, parting the hair four times to look for live nymphs and adult ticks. The moose’s mane is very thick, making it almost impossible to get down to the skin. It’s hard to spot the ticks. They’re small—really small, especially the nymphs.
“In general, this time of year they really only have the nymph stage, but I have seen some adults today, and we want to know if there’s adults on them also."
On this moose, Lazorchak only found about a dozen ticks. That surprised her, because the hair on the top of the moose had been rubbed off, as if the animal had been scratching herself. Jewell and the other hunters confirmed that her skin was like that when they shot her—it wasn’t from being dragged out of the woods. A dozen ticks found in the sampling areas still means this moose had hundreds if not thousands of ticks spread throughout her body.
When moose have a lot of ticks, they often scratch at them. The loss of fur makes them vulnerable to the cold. Moose can sometimes accumulate tens of thousands of ticks by the end of winter. Blood-thirsty ticks can also diminish the blood supply of the animal.
In some parts of the country, including Vermont, ticks are blamed for the deaths of many moose, and may be contributing to a reduction in the population here.
“We take a sample now, and based on the formula, they can figure out what these moose are going to have on them later,” Lazorchak said.
New Hampshire scientists have developed a way to use the data collected in the fall to predict the number of ticks a moose would be likely to have at the end of the winter, when the ticks are at their highest concentration. They use those numbers to determine the likely impact ticks are having on the population.
Though Lazorchak was surprised to see so few ticks on a moose that was showing the effects of a heavy load, the findings on this specimen were in line with what she and others were finding throughout the population. Vermont Fish and Wildlife says that the average tick count for 2014 was about 16. That's a 40% drop from 2013, the first year the department started keeping data. The average count last year was above 27.
"We take a sample now, and based on the formula, they can figure out what these moose are going to have on them later," she said.
It’s an encouraging sign. Fewer ticks mean fewer sick moose. One reason officials think the parasites might be lower this year is because there was significant snow late into the season. Ticks don't survive as well in those conditions.
Tick check complete at the reporting station, Jane Lazorchak moved on to one piece of data that all hunters really want to know: how much does the moose weigh?
Jewell and his companions scrambled around the trailer bed, hooking up the moose to the weighing scale with some heavy chains, then Lazorchak pushed a button on a motor attached to the scales and the moose rose into the air, feet first. 507 pounds.
Not the biggest moose of the year, which weighed in at 919 pounds dressed, but not the smallest either. Jewell said he would butcher the moose and keep the meat for winter.
Meanwhile, all of the data collected by Lazorchak and her colleagues at reporting stations around the state will be tabulated and analyzed to give biologists a better understanding of the dynamics surrounding Vermont’s moose herd. And it will help Fish and Wildlife determine how many moose permits to award next year.