Residents on three of Portland’s islands may hear gunfire during the next several weeks. But officials say there’s no need for alarm – it’s just the city’s annual effort to thin deer herds.

Deer hunts began Thursday night on Peaks, Cliff and Great Diamond islands, said Mike Murray, Portland’s island and neighborhood administrator. The hunters, who are island residents, typically take up their positions in the late afternoon and stay into the evening. The hunt likely will continue until the end of the year, but will not be a daily occurrence, Murray said Thursday.

Special deer hunts, which have the side benefit of filling some freezers with venison, have become a regular part of island life in Maine.

Deer are surprisingly good swimmers and have found their way to islands all along the coast, where they face no threats from predators and gradually grow in number until they virtually overrun the communities. Concerns about deer-vehicle accidents, Lyme disease, which is transmitted by deer ticks, and the devastation of gardens and shrubs by deer have persuaded island residents to allow limited hunts.

Other Maine islands that have allowed controlled hunts include Monhegan, Islesboro and Swan’s islands.

Eastport, an island community of 1,300 residents in Down East Maine, is considering a special hunt after becoming inundated with white-tail deer that roam the streets and graze in backyards.

HARVESTED DEER STAY ON ISLANDS

On Portland’s islands in Casco Bay, pairs of hunters overseen by a retired state biologist will be looking to bag up to 15 deer at designated bait sites on each island.

“These people aren’t wandering around aimlessly through the woods to find the deer,” Murray said, noting that islanders have been notified and signs have been placed near the ferry landings. “The deer are coming to them.”

Phil Bozenhard, the retired biologist who leads the hunts, said he expects a small number of deer will be culled from the populations on each island. They have already taken five from Cliff Island.

The annual deer hunt has been happening since 2000, when Peaks Island became overrun with deer. The deer herds were so large that deer were starving to death and island residents could not maintain gardens.

“The island could not support a deer population of that size,” Murray said.

The harvested deer remain on the islands and are first offered to volunteers who help maintain the bait sites and provide transportation to the hunters, Murray said. Residents who receive the deer are responsible for securing their own butchering services.

The first deer hunt on Peaks Island netted 172 deer over five days in 2000, Murray said.

Deer populations are much smaller today on Portland’s islands, which are home to about 1,000 year-round human residents.

ABOUT 25 DEER ON EACH ISLAND

Bozenhard said there are currently about 25 deer per island on Peaks, Cliff and Great Diamond, but the hunt needs to occur to keep the populations in check. Deer are strong swimmers and can swim between islands.

Peaks Island had a deer population in the 200s before the 2000 hunt, and the deer were so tame they would come up to people and eat out of their hands, Bozenhard said.

With no natural predators on the islands and no regular hunting season, the deer would thrive.

“It was like a little utopia for the deer,” he said.

Staff Writer Joe Lawlor contributed to this report.