It’s not unusual for mainlanders to head over to Peaks Island or some other Casco Bay community in hopes of making a home or raising a family.

Some stay and some don’t.

But it’s not that often that the newcomers are beavers, and they decide to stay on.

Peaks now seems to have two beaver families – or perhaps one family with a guest lodge. The two well-built lodges have appeared near the southeast shore and Trout Pond.

Along with building their lodges using branches, saplings and some pilfered lumber, the beavers have been hard at work on multiple dams. They’ve raised the water in a stream more than a foot and may flood part of Battery Steele this summer, said Garry Fox, a biology teacher at Portland High School and member of the Peaks Island Land Preserve.

Fox and other islanders have been watching the engineering project progress, knowing that destroying the dams wouldn’t discourage the industrious rodents from simply rebuilding. “You can’t beat them in that regard,” he said.

The first of the beavers is believed to have arrived about five years ago. One islander thinks she saw that one, tired and wet, climb out of Casco Bay onto the south shore near Cushing Island.

They seem to like the privacy of island life and keep pretty much to themselves. “They operate, it seems like, at night,” said Fox, who has yet to see any of his new neighbors in the fur.

The islands of Casco Bay are certainly no Galapagos, a cluster of islands off Ecuador so isolated they have their own varieties of bird and turtle species. But the nearly two miles of Atlantic Ocean that separates Peaks from the mainland is enough to give it a different mix of wildlife.

“We don’t have squirrels. We don’t have chipmunks,” said Fox.

Those smaller mammals can reach islands using the life-raft strategy – cling-and-drift – but the odds aren’t good. It’s a much easier journey for larger swimmers, which include moose and deer, a species Peaks has plenty of.

Raccoons can swim, but they’re thick, absorbent coat would get too heavy for a Peaks crossing, said Philip Conkling a naturalist and director of the Island Institute in Rockland. Raccoons do sometimes reach Maine islands involuntarily. “They have been brought out to islands … to be hunted for recreation,” Conkling said.

Someone on Peaks once introduced a raccoon, but it hasn’t been seen for a while, Fox said. Another islander once brought a skunk across, apparently to get the upper hand in some island feud. It was trapped and shipped back ashore, he said.

Coyotes have started swimming to some Maine islands, which worries those who raise herds of sheep offshore, Conkling said.

“From time to time you’ll get a bear on the biggest uninhabited islands,” he said. “It’s hard for them to find a mate, but there’s plenty of food.”

Conkling has seen beavers, or at least their handiwork, on several islands. Some young beavers basically travel so far downstream in search of a new home that they find themselves swimming in one of Maine’s bays.

“They don’t live in saltwater but to migrate through it is not a problem. They’re fully aquatic and they’re strong swimmers,” Conkling said. “They’ve shown up on Vinalhaven, which is 8 to 12 miles offshore.”

But, alas, the story of island wildlife is often one of immigration and extinction, said Conkling. Food and new habitat runs out before too long and it’s time to move on.

Fox, in fact, thinks the Peaks beavers may soon run out of poplar and birch trees to chew on. Then, like a lot of mainlanders before them, they’ll realize island life isn’t for everyone.

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