Beavers famously will industriously build ponds and gnaw down trees , basically until the end of time. This is a good thing, at least until it's too much of a good thing.
In the past, humans hunted beavers to extinction in many places. Now they are being reintroduced, and we are discovering what happens when Beavers aren't hunted. They eat everything, ranging farther and farther from their dens.
This fall, researchers from Minnesota and Manitoba report a study of the wolves and beavers in Voyageurs National Park [1].
Wolves prey on beavers, so the reintroduction of wolves near beavers results in some beavers being eaten.
The basic finding of the study is that, absent predators, beavers will range farther and farther, and harvesting more and more trees. They will eat all the aspens and leave "an evergreen collar around the pond". [2] The researchers describe trail camera footage as "a little beaver conveyor belt", as beavers made trip after trip up and down the trail. (Dr. Thomas Gable quoted [2]).
So…wolves.
Wolves don't have much problem figuring out this pattern, and will start to pick off beavers for lunch. Apparently beavers are pretty big and fierce, so this is more of a fair fight than I would have guessed. Still, when attacked by wolves, beavers need to get back in the water, pronto.
The upshot is that wolves have the most success farther from their pond, i.e., at the far end of the beavers' trails. So, when there are wolves, beavers adjust, and don't range as far, and therefore, don't wipe out as much of the forest.
Other ecologists note that wolves also prey on moose and elk, which compete with beavers [2]. I.e., it's not just simply wolves v beavers. So, to the degree that wolves help keep all the grazers in check, which, overall, helps the forest keep in balance.
In the case of beavers, the presence of wolves probably limits the area of their exploitation, and keeps them near their home ponds. So, wolves as well as beavers are ecosystem engineers.
One researcher called the wolves "permitters", who tell the beaver engineers "nope". So--the big bad wolf, top predator? No. Top bureaucrat is more like it. : - ( Not exactly the stereotype identity of wolves!
- Thomas D. Gable, Sean M. Johnson-Bice, Austin T. Homkes, John Fieberg, and Joseph K. Bump, Wolves alter the trajectory of forests by shaping the central place foraging behaviour of an ecosystem engineer. Proceedings of the Royal Society B: Biological Sciences, 290 (2010) 2023. https://doi.org/10.1098/rspb.2023.1377
- Cara Giaimo, Leave It to Beavers? Not if You're a Wolf, in New York Times. 2023: New York. https://www.nytimes.com/2023/11/07/science/beavers-wolves-forests.html
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