Head of the Harbor Village trustees will move forward with a plan to control the overabundant village deer population with a birth control drug.

“This is the way we want to go,” Mayor Douglas Dahlgard said at a village board work session last Wednesday after the four trustees present gave unanimous approval.

Under a plan sketched out in a report by village residents and experts last month, the village would participate in an experimental program run by The Humane Society using an immunocontraceptive drug called porcine zona pellucida, or PZP, which has shown some success in other areas, including Hastings-on-Hudson, in Westchester County.

Researchers would use anesthetizing darts to bring down female deer, then inject the drug, which must be re-administered after several years.

State Department of Environmental Conservation officials have called the approach “problematic” because it is difficult to execute and may take years to reduce deer population. The department recommends recreational hunting to control deer populations, along with culls carried out by professionals or specially licensed amateurs. However, many village residents oppose killing the animals.

There is no official count of the deer population in and around the village, but the mayor of neighboring Nissequogue, citing conversations with New York State wildlife biologists, recently estimated about 600 deer live in northern Smithtown.

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Deer are struck and killed by motorists on local roads more than once per week, according to municipal highway departments. Here and elsewhere on Long Island, according to the DEC, deer are eating both planted and natural vegetation and are tied to a potential increase in diseases, especially Lyme disease.

Important elements of the plan have yet to be filled in, from the cost to taxpayers to the possible legal complication of government-sanctioned dart-gunning of deer in a village whose code is interpreted by some to ban the discharge of any type of firearm or weapon.

The plan would be subject to state approval and would require the participation of The Humane Society, which sent researchers to the village last month to evaluate its suitability for the program. Humane Society officials are expected to reach a decision in coming weeks.

The village’s Deer Management Committee estimated the cost of the program at $500 to $1,000 per doe, an amount that could drop in coming years if PZP becomes commercially available. Officials of the privately run Avalon Park nature preserve in the village have said the park will share some of the costs. Dahlgard said the village may also seek grants and donations.