LITTLE COMPTON, R.I. — Walking along a stone wall on Roger and Gail Greene’s property — they guessed the structure dates back to the early 1800s or even late 1700s — every rock and cranny is a world unto its own.

A black cherry tree stretched its way up and out from underneath — a gift likely planted by a bird who had perched on its stones decades ago, Roger said. Minty green lichen made splotches on gray rocks. A pickerel frog with skin like a snake hopped its way through leaf litter and low grasses to a hiding space before an ecoRI News reporter could get a good photo.

Stone walls originally marked the boundaries of farms, but now they have become homes to all different types of creatures.

Roger and Gail maintain the walls on their property and at the nearby Simmons Mill Pond Management Area. Every year, they leave out signs for visitors explaining how farmers created the walls using a system of pulleys and levers to dig up and move the stones from cleared fields. (Roger and Gail have some original iron wall-making tools in their shed.)

In addition to showing the history of the stones, they also draw attention to the natural world that has surround the walls, like spring ephemerals that grace the bottom stones for only a few months each spring or the several types of ferns that unfurl almost to some of the walls’ full heights.

Robert Thorson, a professor at the University of Connecticut who started the Stone Wall Initiative, said in his studies of the structures, he has observed tons of wildlife, from big to small.

There’s the lichen visible to the naked eye, but there are also others much smaller. Larger creatures, such as chipmunks and snakes, also like to make stone walls home. Bobcats have even been known to use the walls to their advantage, Thorson said, as hiding places and ambush spots.

Recently, he said someone came to him complaining that the deconstruction of a nearby stone wall was flushing animals out of hiding and onto her property, revealing all that dwells among the stones.

“She’s being invaded by, you know, chipmunks and squirrels and mice, even rats, snakes,” he said. “Everything is just all coming at her because the habitat’s gone.”

Christopher Raithel, a retired biologist for the Rhode Island Department of Environmental Management, said stone walls mimic habitat that wildlife would use in a completely natural environment, like boulders and ledges.

“They’re using it because it happens to be there,” he said, not because it’s the only habitat in which they could survive. “They’re not going to work real hard to find a different place if there’s one right there.”

Raithel said snakes and lichen in particular have adapted well to life in stone walls.

Snakes use walls for thermal stability, sometimes hibernating in the relatively warm environment the stones make during the cooler months. Stone walls that have footings into the dirt and stone foundations tend to be particular favorites.

Gail Greene said they have found ring-necked snakes in both their stone walls and in the stone cellar. (“Don’t get much bigger than this,” she said, marking less than a foot with her hands, “and they have a beautiful, beautiful yellow ring … almost gold.”)

Flat stones, which are found naturally in some areas around the state, including Little Compton, form some of the best habitat for snakes, where they can hide in the tight nooks of the form-fitting rocks, rather than the larger gaps caused by the walls made of rounded stones.

The other frequent flier on Rhode Island’s stone walls are lichen, a life-form created from the symbiotic relationship between a fungus and an alga.

“Stone walls are basically caked with lichens,” Raithel said. They can also be found on some trees and natural boulder formations, but “when the stone walls came along, the lichens adapted.”

Although many of the state’s stone walls are dry — meaning they were created by simply piling stones on each other without additives — walls with mortar attract particular types of lichen that prefer the “favorable chemical conditions” made from lime.

Of the 150 or so visible lichens, Raithel guessed about half can be found on stone walls.

Several of those species were on display at the Greenes’ property, with a range of colors, textures, and shapes.

What appeared to be black wart lichen, which likes limestone, rested on their mortared woodshed, while a bright green species grew against the pink of some local granite.

The pair recently bought a black light to try to spot the phosphorescence of the lichen at night. 

But the brightest color from the lichen they’ve seen in the daytime is aptly called sunburst, a funky orange-yellow species that used to grow on the gravestones next to their home — before the stones were refurbished — but now they more often find on the stone walls close to Little Compton’s shoreline.

Driving some miles to Sakonnet Point from their farm home to show off the sunburst, Roger and Gail pulled over along the way to point out some of the best examples of walls in town.

The grand walls in front of the Town Commons containing a graveyard had lichen that looked as old as the walls themselves, Roger pointed out, though some structures barely peek out from overgrown porcelain berry and nightshade along the road.

The longtime Little Compton residents said that over time, people have come to appreciate stone walls more; they’re beginning to uncover them again and appreciate what they’ve become.