Martha’s Vineyard may soon join a growing list of communities in New England that have taken aim at white-tailed deer as a way to lower the risk of tick-borne illness. But results have varied widely across the region.

“We are learning from the literature,” state deer and moose biologist David Stainbrook told the Gazette this week. “It seems like there is some level where if deer numbers get low enough you’ll start to impact tick numbers, but it’s a very complicated system.”

Ticks carry an assortment of diseases, which they pick up from white-footed mice and other small mammals. And while the deer do not contract most tick-born illnesses, they provide food and habitat at a key point in the ticks’ life cycle – when they are mating and laying eggs. In theory, reducing the number of deer could reduce the number of ticks. But many questions remain.

“We are definitely venturing into new territory,” said Island biologist and unofficial tick czar Richard Johnson. He recently joined with others in calling for deer culling in response to the apparent spread of lone star ticks across the Island. “It’s one of the reasons I am proceeding slowly — I like to make small mistakes and not jump in too fast,” Mr. Johnson said.

Martha’s Vineyard has as many as 60 deer per square mile, according to the state Division of Fisheries and Wildlife — near the higher end of the state range. Up to 90 per cent of the Island is considered deer habitat, although deer tend to congregate in areas where hunting is limited, including private land. Efforts to thin the herd would likely focus on opening up those areas for hunting in the fall.

The Island also lacks coyotes and other predators to keep the deer population in check.

Mark Lovewell

The Island also lacks coyotes and other predators to keep the deer population in check.

Mark Lovewell

“That would be the number-one most effective way to increase hunting access — to start breaking these barriers down,” said Mr. Stainbrook. “That is probably the biggest limitation in management ability.” He added that increased hunting on the Island would not require any special permits, and the state has already increased the number of kills allowed per year.

“You could double the amount of land that’s open to hunting right now and you probably would still have enough permits for everybody,” Mr. Stainbrook said. The big question is how many deer would need to be removed to affect the tick population. Some studies suggest that reducing the number of deer to fewer then 20 per square mile may significantly reduce the risk of tick bites, while reducing it to around eight deer per square mile could interrupt the disease cycle itself. But the thresholds may vary from place to place.

On Crane Beach in Ipswich, reducing the number of deer from around 400 to 100 led to a decline in deer ticks, but a few years later, scientists counted even more ticks than before.

Tamara Awerbuch, an instructor at the Harvard T.H. Chan School for Public Health who has studied the Ipswich project, said there was no linear relationship between deer culling and the number of ticks in an area. The ticks will simply crowd onto the remaining deer, she said, increasing their chances of insemination.

A dramatic crash in the deer population on Naushon in the 1980s, from around 600 to 60 (attributed to predation by coyotes), also did not translate to fewer ticks. Thomas Mather, a professor at the University of Rhode Island, recalled surveying the area with other tick experts following the crash. “We all agreed that we had never seen so many ticks,” he said.

But he also noted that many areas with few deer have few ticks, and places recently invaded by deer have seen ticks become more abundant. “There is a lot of good reasoning that if we then reverse those trends, we should be able reverse the number of ticks,” Mr. Mather said.

Some studies show a link between the number of mammal species and the risk of Lyme disease in an area. With more potential hosts, fewer deer ticks will end up feeding on white-footed mice and other key hosts, potentially diluting the reservoir for disease.

Another study found a link between red foxes (which feed on smaller mammals) and the abundance of Lyme disease, suggesting that a decline in red foxes has led to an increase in the disease. “Lyme disease is notably rare in western New York, where fox are abundant, despite having among the highest deer abundance in the state,” according to the study published in 2012.

Luanne Johnson of BiodiversityWorks in Vineyard Haven said Martha’s Vineyard no longer has foxes, although grey foxes were a native species. The Island also lacks coyotes and other predators to keep the deer population in check.

The unintended consequences of deer culling on the Island are unclear. It’s possible that fewer deer could cause a spike in tick-human interactions in the first two years, since fewer adult ticks would be swept up by the deer. “It may be that they will be on other animals more, including us,” Mr. Johnson said. “But we are not going to suddenly become the host where they go to feed and mate before they lay their eggs. And I don’t think the other animals on the Island are, either. [Ticks] are pretty tightly coevolved with the deer.”

Management efforts often focus on Lyme disease, but deer also play a role in transmitting babesiosis, anaplasmosis and Powassan encephalitis, all of which are carried by ticks and can infect people. They also carry Ehrlichia chaffeensis, the causal agent for ehrlichiosis, which is transmitted by lone star ticks.

Reducing the Island deer population enough to affect the ticks would likely take several years. “I will certainly say I don’t expect it to happen in five years,” Mr. Johnson said. “I think we are going to have to use all the other methods while we work on the deer.”

Managing white-footed mice themselves would likely present an even greater challenge than managing the deer, he said. One option is using so-called tick tubes, which contain fibrous material treated with a tick toxin that the mice carry back to their nests.

At one time, the Island deer herd was treated with four-posters, feeding stations with vertical rollers that attract the deer and apply a tick toxin to their ears and neck. The stations were removed some time ago, following the death of the Cape and Islands tick and Lyme disease specialist who had run the program.

Ms. Johnson of BiodiversityWorks doesn’t advocate for four-posters in general, since they also attract skunks, crows and other animals. But Dan Gilrein, an entomologist with Cornell University, said he has noted a “dramatic decline” in deer ticks in areas of Long Island where four posters were used and maintained.

Mr. Johnson believes the strategy would be too costly to reintroduce on the Vineyard, especially since funding for the Island’s tick-borne illness reduction initiative is expected to run out this year. (The Vineyard Center for Clinical Research in Vineyard Haven, launched in 2014, may provide continued income for the initiative, but has not done so yet.)

Deer culling could be relatively affordable, since hunters would be the ones doing the work. Mr. Johnson also said a program could be set up where the extra meat could be distributed to people in need. “That, to me, is a really important part of what we are doing,” he said. “I don’t believe in going out and killing a deer and wasting it. If the deer is going to die it should go to feed somebody.”

Mr. Mather, who has also studied the sociological dimension of tick reduction efforts in the region, says it’s important to take a long-term view, and not lose sight of simple strategies — such as yard maintenance and body checks — to reduce the risk of infection. Mr. Johnson said the Vineyard was ahead of the game in that regard, with more people becoming aware of the problem in recent years, thanks largely to the tick-borne illness reduction initiative.

He said he plans to reach out to property owners this summer and begin developing a consensus around the deer culling proposal. “I think we’ve got to publicize it more, we’ve got to build an agreement,” he said. “Then we’ve just got to figure out how to do it.”