Monday, March 26, 2018

Stone walls

By Beth Sullivan
This is a good time to get out and begin to stretch our legs and take in the landscape after winter. The woods are open still; the greenery hasn’t yet begun to obstruct our views of the infrastructure of our open space. The rocky ridges, ledges, and even cliffs of some of our more rugged preserves can be most appreciated now. A walk off the trail to get to the base of a slope for a closer look is not likely to be disruptive to nesting animals yet. It’s easy to imagine larger animals taking shelter in the caves and openings created by rocks and boulders.
A pile of shells at the base of a wall or on top of a rock is a sign of a Chipmunk or Squirrel using the safety of the rocks.

Tracks show travel between protective walls in winter.

This Chipmunk sits up high and is never far from an escape into the wall.

Openings in natural ledges and ridges create places for larger animals to shelter.

New England's stone walls

It is also time to enjoy the bones of our landscape, the stone walls that criss-cross both fields and forests in our area. Much has been written about the history of the walls in New England. Much has been debated about their age, origin and the intention of the builders. No matter what the theory, we all agree that the walls are man-made as opposed to the exposed ridges and outcrops that are nature-formed. A great book to read is Stone by Stone by Robert Thorson, which discusses history and construction of walls in New England.
A recent article in the Northern Woodlands magazine, offered me a new reason to look at the stone walls more closely and in a different light. Those walls themselves act as unique ecosystems running through the woods. They can act as highways of travel on various levels. Small mammals like mice, voles and chipmunks can safely move inside, along, on, and under the rocks to travel from one area to another. They will often have their tunnel openings along-side a base rock and several escape routes as well. Chipmunks, in particular, are rarely found far from a safe hole and most frequently they are near walls. Explore along a length of wall in the woods and you may find piles of cracked nuts and acorns. Sometimes they are even atop the highest rocks, which provides a picnic site with a great view, a lookout spot, and if danger threatens from any direction, it is a quick and easy dive for cover.
Even in the depth of winter, the stone walls offer a greater degree of cover and protection. You can often find small tracks leading to and from an opening at the base of a stone wall, whether in the forest or along a field.
Bigger mammals like foxes and coyotes, weasel family members, and bobcats are frequently spotted near stone walls. They know that their prey is often attracted to those areas. But they also like to travel along the top length of the walls. It is quieter than rustling leaves, offers a higher vantage point, and leaves no tell-tale scent on the ground.

It's not a wall, it's a micro-habitat

Stone walls also alter the ecosystem by creating micro-habitats. The sunny side of the wall will retain the warmth of the sun, so very welcome in the early spring. Snakes, such as the Garter snake, which may have hibernated underneath the piles, will often be found basking in the early spring, soaking up the heat of sun warmed rocks. Those same rocks will retain warmth longer into the autumn as well. The Mourning Cloak butterfly, the first to be spotted in the early spring, will often hibernate over winter in cracks and crevices of stone walls, to emerge on a sunny warm day in late March. It will return to the same type place for protection when the winter weather returns, until it is safe to emerge for good.
On the flip side, the shaded side of a wall will retain moisture during the heat of summer. The forest floor can get hot and dry, but amphibians that require some moisture and less intense heat will find themselves drawn to the cool side and damp ground along the base of the shady side of a wall. Wood frogs and Spring Peepers, as well as many salamanders, make use of these areas because the leaf litter that piles up along the wall harbors insects and other invertebrates that they choose to feed on and offers protection as well.
Next time you walk in the woods and encounter a lost stone wall, you can wonder about its origins and usage. But also think about it as a unique mini-habitat for many woodland creatures. Think about how much farther that Chipmunk can travel safely using only the forgotten stone walls in our woodlands.
Bobcats will hunt for small prey along stone walls. Photograph by Rick Newton.

A Garter snake emerges  early to soak up heat from sun-warmed rocks. 

A Spotted Salamander will seek out the cool, moist leaf litter on the shady side of a stone wall.

Photographs by Beth Sullivan, unless otherwise indicated.

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