Beaver-engineered habitats are outperforming ours

Beavers have recently enjoyed a makeover as ecological heroes. Their dams and ponds, once destroyed as a pesky source of flooding, are now hailed as water-cleansing oases that do everything from harbor fish to buffer the landscape from wildfires.

But less has been said about their effects on terrestrial creatures in the surrounding land. It turns out the effects of these paddle-tailed rodents extends well beyond the water’s edge. Recent research by two separate groups of scientists in Europe shows that beavers are a boon to a host of winged creatures ranging from bats to tiny flies.

The new findings have researchers declaring: Bring on the beavers (and their ponds). “Our work adds further important evidence of the beneficial effects of beaver wetlands for wildlife,” said Patrick Cook, an ecologist at the University of Stirling in the United Kingdom.

The work by Cook and his collaborators focused on how beavers might benefit pollinating insects, such as bees, butterflies and flies. They compared the insects found flitting among the foliage around beaver ponds and surrounding wetlands with human-made ponds in a patch of Scottish pasture.

They discovered that hoverflies were more than twice as abundant in beaver ponds and 45% more butterflies were found there compared to the artificial ponds, the scientists reported in the Journal of Applied Ecology. There was no difference for moths or bees. The scientists suspect the difference comes down to what kinds of vegetation occurs in the different settings. The beaver-built wetlands are more dynamic, prone to changes in water level and vegetation as beavers go about their business of damning water and gnawing down trees and shrubs for food and building materials.

That rewards plants that flower faster and with greater abundance, capitalizing on conditions when they are good. That, in turn, creates more opportunities for pollinators. The beaver ponds also had larger numbers of pollinator species that thrive in damp ground and rotting or dead vegetation, all things associated with beaver ponds.

.IRPP_ruby , .IRPP_ruby .postImageUrl , .IRPP_ruby .centered-text-area {height: auto;position: relative;}.IRPP_ruby , .IRPP_ruby:hover , .IRPP_ruby:visited , .IRPP_ruby:active {border:0!important;}.IRPP_ruby .clearfix:after {content: "";display: table;clear: both;}.IRPP_ruby {display: block;transition: background-color 250ms;webkit-transition: background-color 250ms;width: 100%;opacity: 1;transition: opacity 250ms;webkit-transition: opacity 250ms;background-color: #eaeaea;}.IRPP_ruby:active , .IRPP_ruby:hover {opacity: 1;transition: opacity 250ms;webkit-transition: opacity 250ms;background-color: inherit;}.IRPP_ruby .postImageUrl {background-position: center;background-size: cover;float: left;margin: 0;padding: 0;width: 31.59%;position: absolute;top: 0;bottom: 0;}.IRPP_ruby .centered-text-area {float: right;width: 65.65%;padding:0;margin:0;}.IRPP_ruby .centered-text {display: table;height: 130px;left: 0;top: 0;padding:0;margin:0;padding-top: 20px;padding-bottom: 20px;}.IRPP_ruby .IRPP_ruby-content {display: table-cell;margin: 0;padding: 0 74px 0 0px;position: relative;vertical-align: middle;width: 100%;}.IRPP_ruby .ctaText {border-bottom: 0 solid #fff;color: #0099cc;font-size: 14px;font-weight: bold;letter-spacing: normal;margin: 0;padding: 0;font-family:'Arial';}.IRPP_ruby .postTitle {color: #000000;font-size: 16px;font-weight: 600;letter-spacing: normal;margin: 0;padding: 0;font-family:'Arial';}.IRPP_ruby .ctaButton {background: url(https://www.anthropocenemagazine.org/wp-content/plugins/intelly-related-posts-pro/assets/images/next-arrow.png)no-repeat;background-color: #afb4b6;background-position: center;display: inline-block;height: 100%;width: 54px;margin-left: 10px;position: absolute;bottom:0;right: 0;top: 0;}.IRPP_ruby:after {content: "";display: block;clear: both;}Recommended Reading:First global study of the extraordinary role of animals as architects of Earth Perhaps given this proliferation of insects, it should come as no surprise that another group of scientists in Switzerland found that bats—many of whom eat insects—were drawn to beaver ponds as well. At eight rivers with beaver ponds, scientists put out audio recorders capable of detecting the sounds bats emit to echolocate their prey. Recorders situated next to ponds revealed that bats hunted there 2.3 times more frequently than they did in parts of the streams that flowed freely and weren’t inhabited by beavers.

On a typical night, the beaver ponds also hosted a greater variety of bats—on average 5 species versus 4 on other parts of the stream, a 22% difference, the scientists wrote in the Journal of Animal Ecology. I would not have expected such a significant increase in bat numbers, says Valentin Moser, who conducted the study as a Ph.D. student at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. The ponds likely lure bats to them because of the more abundant insects, and because the vegetation there is more attractive to certain species.

For example, the endangered western barbastelle bat sleeps under the bark of standing dead trees, a common feature in ponds where trees die when they are flooded. “The tree trunks remain standing for years and provide a very valuable, because rare, habitat,” Moser said. Much as in North America, populations of the Eurasian beaver, Castor fiber, are rebounding after being driven to near extinction in much of their range by trapping for pelts and because they were long considered a nuisance.

A recent estimate put their numbers at 1.5 million in Europe and Asia. Still, the love-hate relationship between people and beavers means scientists studying their ecological effects are lobbying people to let the animals work their magic on the landscape.

They could, among other things, provide a needed boost for insects and bats that are both in decline. On occasion there may be valid reasons to remove a beaver dam,” said Nigel Willby, a Stirling University ecologist involved in the pollinator research.

“But we should remember that for every beaver dam removed, a beaver wetland dies, along with a multitude of attached benefits, including for pollinators. “Beaver wetlands create a buzz and a flutter for pollinators.” Journal of Applied Ecology. “Habitat heterogeneity and food availability in beaver-engineered streams foster bat richness, activity and feeding.” Journal of Animal Ecology. Photo: Franz Fischer via Flickr