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Keystone Connections – from Beavers: Radical Rodents and Ecosystem Engineers

Beavers belong to an exclusive club of animals called keystone species. In a stone arch, the keystone is a wedge-shaped block that sits at the top of the structure and locks all the other pieces into place. If the keystone is pulled out, the arch collapses––just like a Jenga tower crashes down if you remove a key block. In nature, a keystone species plays a special role in its community, supporting other species and helping to keep the whole ecosystem* functioning properly. If a keystone species is removed, the community it supports is weakened and may break down completely.

Beavers play their keystone role by creating wetlands––including ponds, marshes and swamps––that provide essential habitat for many animals and plants. Wetlands are among the world’s most biologically productive ecosystems, right up there with rainforests and coral reefs. In other words, wetlands are home to a greater variety and abundance of plants and animals than most other ecosystems. And because wetlands are one of the world’s most threatened habitats, many of the plants and animals that live in them are in danger of becoming extinct. In North America, we have beavers to thank for developing and maintaining much of our wetland habitat.

When you visit a beaver pond, it’s easy to see the richness of life that exists there. The first thing you might observe is how lush the surrounding vegetation is. That’s because water from the pond is seeping out into the ground around it, and the thirsty plants are drinking it up. Plant eaters like deer and voles love to browse on the well-watered shoreline greenery. Moose, on the other hand, prefer to wade in deep to feast on water lilies and other aquatic plants.

Dip a net into the water, and you’ll discover that it’s teeming with plankton and insects. These small creatures, some so tiny that you need a microscope to see them, are at the center of the beaver-pond food web. Fish and tadpoles gobble them down and are eaten in turn by herons, kingfishers, minks, raccoons and other predators. As for those mosquitoes that are buzzing around your ears, they’ll get snapped up by dragonflies, frogs, swallows and bats.

Beavers also provide living space and housing for other community members. Beaver ponds and canals offer a wide range of real estate options for fish, amphibians (frogs, toads and salamanders), turtles and semi-aquatic mammals such as muskrats and otters. Trees killed by beaver flooding are equally useful. Woodpeckers drill into the dying and dead trees to make their nest holes. Once they move on, other birds, such as swallows, claim these spaces. For wood ducks and other cavity-nesting ducks like buffleheads, goldeneyes and mergansers, these old nest holes in trees next to beaver ponds are ideal homes. When their ducklings are ready to leave the nest, they can launch straight out the front door of their high-rise residence and drop into the water.

The list of species that depend on beavers and their engineering work varies from place to place. A beaver pond in Arizona hosts different plants and animals than one in the Northwest Territories, for example. But no matter where they’re found, beaver habitats are always lively places with a large cast of characters.

* Words in bold italics are glossary terms.