Scientists have discovered that insect-eating bats have a very handy ally in European forests: the beaver. Bats reap real benefits as beavers transform the landscape by felling trees and building dams. In short, BBC reports, new research shows that "beavers construct ideal habitats for bats."
By felling trees, beavers thin out the forest canopy, removing obstacles that get in the way as bats pursue their flying-insect prey, reporter Ella Davies writes.
Scientists from the University of Gdansk in Poland undertook their study to demonstrate that European beavers, which were extinct in Poland until their reintroduction after World War II, are important in maintaining healthy woodlands.
This research, led by Mateusz Ciechanowski, was published in the European Journal of Wildlife Research.
The team used acoustic bat detectors to monitor bat activity along areas of woodland streams that had been modified by beavers, and other areas where beavers were not present. They found that aerial hawkers – bats (or birds) that hunt flying insects – were significantly more active around the beaver-modified streams. The study involved three pipistrelle bat species, plus common noctules.
Ciechanowski told the BBC that, while bats are agile flyers, their insect-hunting abilities are sharply reduced in very dense forests. Aerial-hawking bats use the biosonar system called echolocation when hunting: they bounce sound off their prey and listen for the echo to pinpoint the insect's location.
The "clutter" of branches in thick forests interferes with echolocation, he said, making hunting less effective, the BBC reports. The remodeling done when beavers cut down trees likely opens up the forest canopy and improves hunting.
In addition, he told the BBC, beaver dams create waterlogged areas that attract insect prey favored by bats. "Forest that was both flooded and subjected to beaver 'logging' supported the highest bat activity," says Ciechanowski said.
On the other hand, the scientists were surprised to find that the beavers' work provided no benefit to bats that forage over the water – in this case, Daubenton's myotis.
Daubenton's myotis use the flat surface of water as a sort of "acoustic mirror" that reflects echocation calls to reveal insects on or near the surface, the BBC said. The researchers had expected that beaver ponds would provide excellent conditions.
Unfortunately, he told BBC, beaver ponds are quickly coated with duckweed, which interferes with echolocation, "masking echoes reflected from flying insects."
But for most bats of Polish forests, beavers are very handy to have around.