Why do beavers seem to go after the tallest, oldest, most magnificent trees? If they ate them, I could understand. But all they do is nibble at the inner bark and then go take down another. What is going on?
• It only seems like they fell the largest trees. Beavers mostly take down small saplings, which provide the most nutrition for the least work and are easily transported. But we generally don’t notice these small fellings, while the larger trees, primarily felled as construction materials, are easily seen and will last for a long time.
David Rubin
Ballston Lake, New York, US
Advertisement
• Beavers can fell the biggest trees. They generally don’t, but every so often they do take down a much bigger tree than you would expect. They sometimes walk straight past a seemingly good, smaller tree that would be much easier to fell in order to reach a bigger tree. On the surface, this doesn’t appear to be the best use of calories.
So why do they do it? Felled trees produce shoots from their trunks and stumps, and beavers like to eat fresh shoots. Taking down a large willow generates a huge amount of regrowth that the beaver will then come back and feed on. It is like farming.
The beavers probably benefit indirectly too. By taking big trees down they have a profound effect on their environment. If the felled tree ends up in the river, for example, it is more likely to push the river out of its banks to flood the surroundings. This means you end up with a more complex wetland, which increases the open water habitat and overall food resources in the long term.
In the UK, we have Eurasian beavers (Castor fiber), whereas the question is from a reader in the US, which has the North American beaver (Castor canadensis). But the two species have a very similar impact on the environment.
Mark Elliott, leader of the Devon Beaver Project,
Devon Wildlife Trust, Exeter, UK
We pay £25 for every answer published in ¿ìè¶ÌÊÓƵ. To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
¿ìè¶ÌÊÓƵ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
You can also submit answers by post to: The Last Word, ¿ìè¶ÌÊÓƵ, 25 Bedford Street, London WC2E 9ES.