Data from a New Hampshire project that put collars on around 36 moose calves revealed that almost 75 percent of them died from ticks, shedding light on the battle between moose and ticks and the apparent upper hand currently held by the blood-sucking insects.
"It doesn't bode well for moose in the long term if we continue to have these short winters," said moose biologist Kristine Rines.
Winter ticks thrive in shorter, milder winters, and during these periods they latch onto moose and feed off of the large mammals. Just one moose can host up to 75,000 ticks on its body, and by the time spring rolls around, many of them become so weak and starved that they die. Only at this point do ticks finally release their grip and continue on to their next host.
The new data marks the second straight year of a high mortality rate for moose calves, although Rines believes that a lower moose density will help the calves since ticks depend on this density along with short winters in order to survive.
"As our moose numbers decline, the ticks will decline, as well," she said. "What we don't know is at what point will things level off."
"The winter tick is on the moose all winter up until right now when moose are molting and shedding their winter coat and so the three life stages, larvae, nymph and adult are all operating at the moose, taking blood meals on those three occasions," added Maine's moose biologist Lee Kantar.
The team used net guns and tranquilizer darts to capture and collar the northern New Hampshire moose that were examined in the study. Furthermore, blood and other samples were collected in order to evaluate their health.
Collared animals that are still alive will continue to be monitored as long as the collars keep transmitting, and when they die, a special signal alerts researchers so that they can get to the location as soon as possible.
"We've got a long way to go before we've got specific answers, but we're trying," Rines said.
In addition to New Hampshire, Vermont has also noticed the effects of winter ticks on moose mortality. Although the state has less to worry about given the lower moose density in the region, biologists have still expressed concern.
"We pay very close attention," said Vermont moose biologist Cedric Alexander. "We're very interested and alarmed when we see that kind of mortality in a collared animal study next door."
