Beavers build dams in the water from dead wood, creating habitats for themselves and many other species. But it’s not just aquatic life that benefits from landscape architecture, but also land-dwelling animals. This even includes bats, as a new study shows. Accordingly, around twice as many bats hunt in areas with beaver ponds as elsewhere – partly because there are more insects than food there. There are therefore more bat species in the beaver areas, including more endangered species.
There are currently over 1.4 million beavers (Castor fiber) living in Europe. These animal forest workers are known for felling entire trees with their gnawing teeth and damming streams with the wood. Near these dams, the beavers then build their dome-shaped castles with internal caves and entrances that are under water. In addition, the rodents change the flow speed and water balance in their environment and thus create new habitats and food for other creatures. It is known that many aquatic organisms benefit from the landscape architecture of beavers, for example fish.
How do beavers change life on land?
But how does the construction activity of beavers affect animals and plants on land? A team led by Valentin Moser from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL has now investigated this. To do this, the researchers compared two sections of eight rivers in the Swiss Plateau: one with a beaver dam and another around 500 meters away without beaver influence. In these areas they analyzed how many flying insects and bats there are. To do this, Moser and his colleagues recorded the echosounder calls of bats hunting insects and caught insects with special traps just above the water surface. They also compared how many standing and lying dead trees there are in the areas, which plant species grow there and how dense and high the tree crowns are in the forest.
The result: The researchers counted more bats in the river sections dominated by beavers. On average, five species of bats occurred per night in beaver ponds and four species of bats in the unchanged river sections, as the team reports. Among them were endangered bat species that are on the red list and were also more common in beaver ponds. Overall, the bats flew through the beaver territories 1.6 times more often. In addition, they hunted there 2.3 times more often than in the nearby control areas, as the researchers determined based on the echo sounder calls.
Paradise for bats
The evaluation also showed that more insects and more diverse plants occur in beaver territories. There is also more dead wood and a more open tree population. These factors attract the bats because they provide them with food and places to sleep, the team explains. “The quality of the habitat is better in beaver areas and the amount of food is higher than outside,” says Moser. Dead wood had the greatest influence on bat diversity. The team cites the pug bat as an example. This endangered bat species sleeps under the peeling bark of standing, dead trees. Such trees are more common in the beaver systems because they die in the dammed water. “The tree trunks stay there for years and offer a very valuable, because rare, habitat,” says Moser.
The researchers conclude from their observations that beavers can act as natural supporters and help protect endangered species such as bats. “Almost all bats are endangered and are on the red list. They need support and the beaver seems to do exactly that for us,” says Christof Angst from Switzerland’s national beaver office at info fauna. “The beaver is once again creating functional, very species-rich and resilient waters, cheaper and better than humans with engineering skills and excavators.” The Beaver Center is now summarizing the findings and developing concrete recommendations on how beavers and their habitats in Switzerland should best be protected in the future.
Source: Swiss Federal Institute for Forest, Snow and Landscape Research WSL; Specialist article: Journal of Animal Ecology, doi: 10.1111/1365-2656.70136