So many deer have moved into the northern Smithtown villages of Nissequogue and Head of the Harbor that they have eaten up the woodland ground cover, denuding gardens and forest that used to provide shelter and food for smaller animals.

Interactions with humans, rare a decade ago, are now common and sometimes fatal for the deer, who are struck by cars on winding, unlit roads. Enough deer have become trapped on swimming pool fences in Head of the Harbor that officials have notified residents of the potential for “deer impalement.”

The two villages sit next to each other on Stony Brook Harbor and share a wildlife-friendly layout of large, wooded lots. But they are exploring very different management strategies for deer, which Nissequogue Mayor Richard Smith estimates at 600 in the northern part of Smithtown: hunting in Nissequogue, and contraception, along with other nonlethal measures, in Head of the Harbor.

These efforts follow a number of others taken to reduce Long Island’s population of 25,000 to 36,000 deer: hunting in Southold, culls in Smithtown state parks, fencing on the Fire Island National Seashore and surgical sterilization — at a cost of $200,000 — in East Hampton Village.

Nissequogue already allows bowhunting of deer on the property of consenting landowners, and last year hunters killed about 48 deer. “That’s not enough,” Smith said, citing New York State statistics that deer populations double every two to three years.

“It’s only a matter of time before it becomes a horrific situation,” he added.

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Nissequogue officials are in talks with the state, which regulates hunting, to extend the season or issue special permits that would ease bag limits and allow for deer to be killed outside the normal season.

Next door in Head of the Harbor, a residents’ Deer Management Advisory Committee is recommending participation in an experimental Humane Society program using PZP, a protein taken from pig ovaries, to chemically sterilize does in the village.

Village officials last year proposed lifting a decades-long ban on bow hunting, but backed off after strong opposition from residents.

Many who live in the village fear trespassing hunters or being shot by errant arrows, the committee found in a survey earlier this year. Other residents oppose hunting on principle: “These deer are a beautiful part of our village. No one should hunt them,” one person wrote in a survey answer.

Inoculation could cost $500 to $1,000 per doe, the committee found, though some of the cost could be shared with the Society. Residents say that other municipalities have paid far more to professional hunters, with little effect.

“Lethal means are expensive and don’t work well,” said Eric Stubbs, a committee member. “Right now we don’t even have money for roads: There are priorities other than killing deer.”

Leslie Lupo, a wildlife biologist for the state’s Department of Environmental Conservation, which favors recreational hunting to manage the deer population, called the PZP approach “problematic.”

Does must be re-dosed periodically and the approach would take years to have an effect, she said.

For now, nobody seems to know whether hunting or contraception, carried out side by side, might provide a comparison test or simply interfere with each other.

The test subjects, as Smith says, aren’t known for being cooperative: “Deer don’t know municipal boundaries.”