The Oxford Dictionary defines a keystone species as “a species on which other species in an ecosystem largely depend, such that if it were removed, the ecosystem would change drastically”. That is certainly true for the beaver. Beavers create and maintain habitat for a wide range of other species, but as a herpetologist (someone who studies reptiles and amphibians) in Vermont, I am going to focus only on a few of the snakes, turtles, frogs, and salamanders that use the habitat created by beavers.
A salamander that has co-evolved with beavers is the Eastern Newt. As an adult, the Eastern Newt lives in the pond created by beavers. But beaver often run out of their favorite foods and move upstream, downstream, or perhaps to a different drainage. If the beaver dam rots and breaks, these adult newts will no longer have a home, but their offspring, the bright orange Red Efts have the job of traveling on land to find a new pond. As they mature and become aquatic, they then can colonize the new pond. If their original pond still exists, they can move back into that one. Red Efts move on land when the ground and vegetation are wet. I suspect many readers have had the experience of walking in the woods after a rain and seeing dozens of beautiful Red Efts. When the ground dries out, the Red Efts will hide under cover objects to conserve their moisture.
Another salamander that often lays its eggs in beaver ponds is the beautiful Spotted Salamander. This is the large (up to 8 inches) black salamander with bright yellow spots that migrates to breeding ponds in the spring. A month or so later, their eggs will hatch and the larval Spotted Salamanders will spend the summer in the beaver pond eating insect larvae and anything else that moves and that they can fit in their mouths (including their family members). In the late summer and early fall, they will leave the pond and head into the nearest woods.
If I am looking for a Pickerel Frog, I will search for a beaver meadow. Beaver meadows are the areas that were once under the water of a beaver pond. If the beavers stop maintaining a dam, the dam will eventually leak or break and much of the pond will disappear, leaving a grassy meadow. These meadows are the perfect hunting habitat for Pickerel Frogs. These beautiful frogs will search for and eat the grasshoppers and other insects that are feeding on the grasses. Adult Pickerel Frogs will lay their brown and yellow eggs in any remaining beaver ponds. Their tadpoles will spend the summer in the pond and in the fall, they will metamorphose and head out into the beaver meadows.
Green Frogs spend most their days in and near ponds, including beaver ponds. They travel on land to feed on rainy nights but will return to their home ponds as the ground starts to dry out. Since Green Frog tadpoles up here in the north country take more than one season to get large enough to metamorphose and leave their ponds, their tadpoles can be found in the pond throughout the winter.
Gray Treefrogs will spend most of their days up in trees and shrubs near ponds. Up in those trees they feed on the insects that live up there with them, but in late spring, they come down out of their trees and shrubs, to lay their eggs in beaver ponds and other types of ponds and marshes.
Within a year or two of its creation by beavers, Painted Turtles and Snapping Turtles may find a new beaver pond and move in. If the pond is deep enough, they may spend the winter there as well.
The open, sunny, beaver meadows are excellent habitat for many of our snakes. Common Gartersnakes and Red-bellied Snakes are two of the snake species I find most often in beaver meadows. During much of the day these snakes hide under cover objects such as logs, or pieces of bark, but if they get cold, or need a meal, they will venture out to bask in the sun or feed on slugs, snails, worms, and the amphibians that breed in the beaver pond.
These are just a small sample of the many species that benefit by the work of beavers. At one point in our history beavers were so reduced in numbers by habitat loss and trapping, that they needed to be reintroduced into Vermont. We are fortunate to have this keystone species once again in our state.
Clockwise from the upper left: an Eastern Newt in the Red Eft stage, photo from the Vermont Herp Atlas; a Spotted Salamander, photo taken by Toby Alexander; a Pickerel Frog, photo taken by Kiley Briggs; a Gray Treefrog, photo taken by Kate Kelly; Painted Turtles basking, photo taken by Jay Plotkin; and a Red-bellied Snake, photo taken by Kate Kelly.