NH moose are under a tick attack. Could changing the way forests are logged help save them? 

In fall, hoards of winter ticks latch on to New Hampshire’s moose — sometimes upward of 50,000 per adult animal.

Over the course of the winter, the ticks drink their fill of blood, weakening adult moose and sometimes killing calves. 

“Essentially, they get the life sucked out of them,” said Henry Jones, New Hampshire Fish and Game moose project leader.

This onslaught, bolstered by climate change, is a major factor behind the ongoing decline in the health and numbers of New Hampshire’s moose over the last two decades, Jones said. So far, researchers have been unsure how to help. But a team of New Hampshire researchers have a new hypothesis: Could the way forests are logged make moose more, or less, likely to encounter parasites? 

A new study, approved to move ahead by the Governor and Executive Council on Wednesday, June 3, aims to answer that question — and determine whether a different approach to forest management could help “zombie moose” evade the parasites draining them of life and energy. 

Of the challenges that moose — and moose researchers — face, the winter tick problem is “a tough one,” said University of New Hampshire professor Remington Moll, one of the study’s leads.

Winter ticks, research by UNH and New Hampshire Fish and Game has shown, are the driving force behind years of decline in Northeastern moose populations. Native to New Hampshire, the species targets moose and other ungulate species, such as deer. They seek out their hosts in the fall, extract up to a milliliter of blood per tick over the course of the winter, and drop off again come spring. 

In recent decades, parasitism of moose by winter ticks has boomed, aided in part by climate change, as longer stretches without snow cover give the ticks more time to find a host, Jones said. 

“The way climate change is affecting moose is through parasites,” he said. 

But while climate change is augmenting the problem, another major driver was a boom in the local moose population, which peaked in the Northeast in the early 2000s, Moll said. The sheer abundance of hosts helped tick populations in the region reach the high levels they remain at today.

The heavy parasitism that results can be debilitating for New Hampshire’s moose. Loss of blood weakens adult moose, reducing the amount of offspring they can produce; for calves, it can be deadly. Weakened by tick parasitism over the course of their first winter, heavily infected calves suffer from anemia and nutrient deficiency. Winter ticks are the leading cause of death for calves under one year, according to the Maine Department of Inland Fisheries and Wildlife. 

Finding a way to help combat the parasites is in the best interest of New Hampshire’s tourism industry, hunting culture, ecological stability, and moose themselves, New Hampshire Fish and Game Executive Director Stephanie Simek and Business Division Chief Kathy LaBonte wrote in a letter to the Governor and Executive Council regarding the project. 

So researchers, said Jones and Moll, are turning their attention to determining if anything can be done to slow or turn around the moose decline. 

One option is raising hunting quotas to reduce the number of moose on the landscape. The hope is that this would reduce the tick burden on moose simply by providing the parasites fewer hosts, Jones said. 

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To this end, New Hampshire Fish and Game has raised target moose harvests in northern New Hampshire, he said. But research on this approach, which other states are also embarking upon, is lacking, so it’s not yet clear whether the tactic will be effective, Moll said.

Another line of attack is the use of pesticides. Tick-toxic chemicals could be applied either to the landscape or to moose themselves to reduce the parasite burden on the animals, Moll said. But this idea, he said, is riddled with challenges.

“If you can get a moose and put [pesticide] on the moose, it helps,” Moll said. “But it’s just logistically very hard. And conceptually, it’s kind of a non-starter, because you don’t want to be putting pesticide everywhere in the forest.” 

But there’s another idea for a way to reduce the tick burden on New Hampshire’s moose, the researchers said, that has not been extensively studied: managing their habitat.

Moose like young forests, where food is plentiful, including areas that were recently logged. Because logging is often done one substantial tract at a time, the researchers wondered, might moose be returning to the same sites each fall and spring to eat — and, at the same time, dropping and picking up ticks again and again? 

Winter ticks don’t travel very far during the summer season, after they have dropped off their hosts, Moll said. So it’s possible, he said, that if the moose are returning to the same locations over and over to feed, they are making it easier for ticks to find them.

In the study, Moll, Jones, and other researchers will use GPS collars and collect tick samples throughout moose habitat to try to determine if that is, indeed, what is happening.

The researchers hope to learn whether moose return to the same location year after year, and what kinds of forest ecosystems are most concentrated with ticks. 

If their hypothesis is proven true, Moll said, it could open up a new route to helping moose by encouraging forest management changes, like more dispersed logging. This could make the tracts of young forest that researchers suspect draw moose spread more widely throughout their habitats, making it more likely that they vary their routines and less likely they pick up ticks. 

While initial work on the project will begin this summer, the researchers will not begin to collar moose until more than a year from now, Moll said.

Three-quarters of the cost of the project, which totals about $1.2 million, will be funded with a federal grant from the U.S. Fish and Wildlife Service. The remaining 25% of the funding will come through the University of New Hampshire.

Jones said learning more about the pressures on the state’s moose population, and whether anything can be done to help them, was a crucial continuation of the work that the New Hampshire Department of Fish and Game and the University of New Hampshire have already undertaken. 

The study will provide important information to widen scientists’ understanding of the many factors that impact the iconic species, Moll said. 

“The forest angle is the one that hasn’t fully been explored. We don’t know if there’s going to be a strong connection or not, but it’s important to pursue that question because it’s never really been answered,” he said. “… We love moose, and we want to figure out what’s going on with them so that we can adjust management and conservation efforts to keep them around.”