STÉPHANE HERZOG We let biologist Cécile Auberson lead the way. She is taking us to beaver territory, in Zumholz (Fribourg), on the banks of the Sense. “This is one of the rare Swiss rivers to have been left in its natural state,” explains the scientist, who works for the national beaver centre of the info fauna foundation. In this region, the river’s path is dictated by its currents, forming braids, to use the technical term. We walk alongside the Dütschbach, a small tributary of the Sense, crossing over wooden walkways. In the heart of this wooded area, where temperatures are pleasant even during the heatwave, we arrive at the edge of a large lagoon. Better than engineers This is a typical beaver reservoir, formed when the animals build dams. “They use their front paws to place mud at the base of their dams,” explains Auberson. Close by is a lodge, which houses a family of beavers. They will emerge at nightfall. Why do these mammals create aquatic areas? Beavers go underwater to reach their lodges, which keep them safe from their predators, including lynxes (which live in the region) and, in other regions, wolves and foxes. These mammals, which can stay underwater for 15 minutes at a time and build their dams in unpredictable places, sometimes flooding roads and fields, Beavers are recreating wetlands destroyed by humans Beavers, which were once killed for their pelts and their meat, were reintroduced in Switzerland from the late 1950s. The dams they build enclose bodies of water that trap CO2, absorb pollutants and promote biodiversity. Their habitat includes the banks of the River Sense in Fribourg. need an aquatic environment at least 60 cm deep to survive. The water takes some of the weight off the occasionally massive pieces of wood they use to build their homes. “Beavers are more effective at creating wetlands than engineers,” observes Marie Bessat, who is in charge of the rural nature programme at the Geneva Cantonal Agriculture and Nature Bureau. The image of these animals has changed radically since they disappeared from Swiss territory in the early 19th century and began to be reintroduced in the late 1950s. Beavers used to be hunted for their pelts (which were used to make hats), their meat and their castoreum, an oily secretion used in medicine. In addition, beavers paid the price for mankind’s widespread expropriation of lakes and rivers. Most of the rivers, deltas and marshes in Switzerland were drained or rerouted to make room for farms and houses. Prior to this forcible redirection, Swiss rivers were dotted with logjams: floating wood barricades, mainly created by beavers. The American journalist Ben Goldfarb tells the story in a book published in 2018 devoted to the resurgence of beavers. The River Skagit, in the state of Washington, “looked less like a river and more like a massive floating sawmill. These piles of wood were not a nuisance; on the Beavers build dams where they want. Beavers were killed for their fur. Their revival has led to more wetlands being created. Photo: info fauna Swiss Review / October 2026 / No. 4 24 Nature and the environment
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