Selectmen in Oak Bluffs and Chilmark last night threw their full support behind a plan to add a second two-week shotgun season for deer in January next year.

Reducing tick-borne illnesses by reducing the deer herd is the goal, Island biologist Richard Johnson told the two boards in back-to-back discussions Tuesday.

Mr. Johnson has led a long-term study of disease-carrying ticks and their natural habitats for the six Island boards of health for the past six years. This week he embarked on a six-town tour seeking approval from Island selectmen to add a second shotgun season for deer next January.

“We are at the point now where we have to do something,” he told the Chilmark selectmen.

“I’m very happy that you’re here,” Oak Bluffs selectman Greg Coogan told Mr. Johnson during his earlier appearance in that town. “I think we all thought we’d never be in this position.”

Speaking before both boards, Mr. Johnson summarized some of the findings of his work, including:

• An Island deer population roughly twice the state average (40 deer per square mile compared with 15 to 20 deer per square mile on the mainland).

• An annual harvest by hunters (both bow and shotgun) that has not increased despite the fact that the state has made doe permits more easily available.

• Tick-borne illnesses that have reached epidemic levels, chief among them Lyme disease, a pernicious bacterial infection that can cause debilitating symptoms if left untreated.

“It seems like the most feasible and most likely to be effective [plan] is to reduce the number of deer on the Island,” Mr. Johnson told the Chilmark selectmen. “The real issue for me is how many people are getting sick.”

He said the idea of the extra hunt grew out of discussions with David Stainbrook, a deer and moose biologist at Mass Fish and Wildlife. Letters from selectmen in every town are a prerequisite for the state agency to consider the request to add a two-week hunt next January. Statewide, deer hunting is allowed in a six-week bow season in late fall, followed by a two-week shotgun season. There is also an antique firearms season for a few weeks in December.

A plan to reduce the deer herd on the Vineyard has been under discussion for some time by the Islandwide boards of health. A Gazette survey done last summer in cooperation with the boards of health found strong public sentiment in favor of culling the herd as a way to control Lyme disease and other tick-borne illnesses.

Selectmen in both towns this week expressed unanimous support for the idea of adding another hunt in January. They also expanded on the discussion, questioning Mr. Johnson about an array of facts and the logistics of conducting a hunt.

Mr. Johnson said current estimates put the deer population on the Island at about 4,000. Hunters take 600 to 800 deer annually, both by shotgun and bow and arrow. “If you go back and look at the numbers of how many deer are harvested on the Island every year, it’s pretty consistent,” he told the Oak Bluffs selectmen. He said a reasonable goal is to reduce the herd from 4,000 to 2,000. “We need to get it below 20 per square mile,” he said. “That’s when you reduce incidence of tick-borne illness.”

He reiterated the well-documented science that deer play a key role in the tick life cycle, acting as a host during the reproductive stage.

“Adult deer tick females feed on the deer and the males are on the deer looking to mate. They lay eggs, that’s what starts the whole cycle,” he said.

He emphasized that the goal is to reduce the deer herd, not eradicate it.

“We can have the deer,” Mr. Johnson said, answering a question from one Oak Bluffs selectman about how he responds to animal rights activists on the sensitive topic. “They’re beautiful animals. They can be here, but it needs to be safe for us to go in the woods.” And he said he has heard increasing support for reducing the herd from Islanders, with “people saying ‘I never thought I would say this, but my kid got sick this year and I’m ready to do something about the deer.’”

Mr. Johnson also said hunting is an important part Island culture.

“For a lot of people hunting is an important part of being on the Island,” he said. He noted that many Island hunters are older. “We can’t lose the hunters. We need to have more hunters,” he said.

January is seen as a good time for an extra two-week season, Mr. Johnson said, in part because the deer have settled down from the fall/early winter hunting season, and also because more houses are closed for the deep winter months, potentially opening up more property for hunting.

Chilmark selectman Bill Rossi said an added hunt could be a small boon to hotels and lodging places on the Island in January.

He also said he had heard of islands in Maine where deer have been eradicated, and there is no more Lyme disease.

“Not everyone is going to be in favor, but I’m favor of culling the herd significantly,” Mr. Rossi said.

In Oak Bluffs, Mr. Coogan echoed the sentiment.

“The time is right,” he said.

Both towns will send letters of support for the initiative to the state.

Mr. Johnson plans to visit selectmen in Edgartown, Tisbury, West Tisbury and Aquinnah next week.