Beavers as Engineers of Wildlife Habitat

Abstract

Beavers are ecological engineers but also keystone species, whose presence in the boreal forest is critical for creating and modifying habitat for a myriad of other species. Beaver impoundments are used extensively by moose and white-tailed deer for feeding, cooling, predator avoidance, and relief from biting insects. Gray wolves focus use on beaver impoundments when preying on beavers, moose, and deer. Wolves also use beaver meadows for rendezvous sites and abandoned lodges for den sites. Several other species of semi-aquatic mammals and mesocarnivores have been reported using abandoned lodges and dams for den sites. Beaver impoundments produce a diverse array of environmental features that provide habitat for many different bird guilds or functional groups. Trumpeter swans and other waterfowl are attracted to open water habitats created by beaver impoundments. Great blue herons and osprey nest almost exclusively on dead trees killed by beaver-flooded forests. Woodpeckers and other cavity nesters also benefit from dead trees in flooded areas. Beaver meadows are attractive to many passerine species that prefer shrubby or grassy habitats. Open water in ponds also provide excellent habitat for amphibians and turtles. In combination, the effect of beaver activity on terrestrial vertebrate diversity in Voyageurs National Park is impressive. Inventory, monitoring, and research efforts at Voyageurs National Park from 1973–2016 documented ≥124 species of terrestrial vertebrates using portions of beaver-affected wetlands for at least part of their life history, representing at least 61% of mammals, 30% of birds, 100% of amphibians, and 20% of reptiles species extant in the park. More directed inventories at beaver impoundments would likely increase these estimates. Future assemblages of terrestrial vertebrates in this boreal ecosystem will change as beaver abundance and their resultant influence also changes across the landscape.