{"id":28718,"date":"2023-06-23T11:22:44","date_gmt":"2023-06-23T09:22:44","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=2753"},"modified":"2023-06-23T11:38:31","modified_gmt":"2023-06-23T09:38:31","slug":"why-do-beavers-build-dams","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/why-do-beavers-build-dams\/","title":{"rendered":"Why do beavers build dams?"},"content":{"rendered":"

No, beavers don’t actually live in dams \u2013 but they still serve a special purpose. <\/p>

By Thomas Ling\n \t\t<\/p>

Published: Friday, 23 June 2023 at 12:00 am<\/p>

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Beavers. If you know anything about them, it\u2019s that they\u2019re brilliant builders, capable of engineering the most complex riverside structures \u2013 no crane or hard hat required. But why do beavers build dams in the first place?<\/p>\n

Answer: Beavers build dams to protect themselves from predators, such as bears or wolves. Beavers don\u2019t actually live in the dams, but in the deep pond of water that dams create.<\/p>\n

In this pool, beavers construct their real home: a small protective island or dome \u2018lodge\u2019 that serves as a dry living area and food store.\nNot only are these ponds deep enough to deter land animals, but they also allow beavers to dig underwater entrances into the lodge. This means that if danger emerges, they can safely exit or escape through these tunnels.<\/p>\n

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A beaver dam (L) and lodge (R). Photo by Getty<\/span><\/figcaption><\/div>\n

Lodges in the UK can be a whole 10m across, requiring dams around 100m in width. The world\u2019s biggest dam \u2013 discovered in Alberta, Canada \u2013 measures a massive 500m in length and could get several hundred meters longer if it connects with nearby dams in future. Contrary to myth, however, it can\u2019t actually be seen from space.<\/p>\n

Interestingly, while these structures guard beavers against large predators in other parts of the world, they\u2019re often not put to the test in the UK. Why? Well, there aren\u2019t really any large predators left.<\/p>\n

\u201cFrom brown bears, to wolves, to wolverines: they\u2019ve all basically been killed off in this country,\u201d explains Richard Brazier<\/a>, Professor of Earth surface processes at the University of Exeter. \u201cBut despite that, beavers are still innately driven to create deep water dams to feel safe.\u201d<\/p>\n

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A beaver dam and lodge. Photo: Getty<\/span><\/figcaption><\/div>\n

So, with the basics covered, chances are you\u2019re now poised with a stream of related questions. From how long dams last for, to what food beavers eat inside their lodges, you can find a (river)bank of answers below.<\/p>\n

What do beavers eat?<\/strong><\/h2>\n

As you might have guessed, The Lion, the Witch and the Wardrobe<\/em> got it completely wrong: beavers don\u2019t eat fish and chips. Not even on Fridays.<\/p>\n

\u201cAlthough otters eat fish, beavers are herbivores \u2013 they generally just eat the leaves of trees such as willows and aspens,\u201d says Brazier.<\/p>\n

\u201cBeavers sometimes also strip trees of bark and eat that. Overall, they\u2019re pretty adaptable and can consume most aquatic plants and vegetation.\u201d<\/p>\n

After finding food, beavers have a clever way of creating a shortcut back home. Having located a particularly scrumptious willow tree, for instance, a beaver may dig out a small canal through the riverbank that leads straight back to their dam.<\/p>\n

\u201cThis means after reaching the tree they\u2019re interested in, beavers can then strip a branch and float it back along the canal for later,\u201d explains Brazier. \u201cIt\u2019s quite ingenious really.\u201d<\/p>\n

How many beavers live in a dam?<\/h2>\n

There\u2019s no set number \u2013 a dam and lodge could hold anything from a pair of beavers to 10. However, generally, only one family of beavers live in one area (they\u2019ll even fight other families that wander into their territory).<\/p>\n

Interestingly, one dam can host generations of beavers, with lodges standing as long as beavers are active in the region. For example, although beavers live for eight years on average, it\u2019s believed the aforementioned dam in Alberta was first constructed in 1970.<\/p>\n

Do beavers hibernate?<\/strong><\/h2>\n

Like many other rodents<\/a>, no, beavers do not hibernate. But they do meticulously prepare for long winter months. In fact, just in case they get frozen into their pond, beavers create a food store below their lodge.<\/p>\n

\u201cIf the pond freezes and the beavers are effectively stuck there, they\u2019ll rely on their underwater food larder,\u201d explains Brazier. \u201cThey can swim out of the lodge\u2019s underwater exit, pick up some willow from their stash and bring it back upstairs.\u201d<\/p>\n

Beavers not only spend more time in their lodge to escape the cold during this time, but also to nurse their newborns, who are normally birthed in winter. And just in case you\u2019re wondering: yes, they are extremely cute.<\/p>\n

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A baby beaver (known as a kit) \u00a9 Getty<\/span><\/figcaption><\/div>\n

What happens if the water level rises too far in winter and the lodge gets flooded? Beavers will just build another layer on top.<\/p>\n

\u201cBeavers have been known to build lodges with five or even ten stories,\u201d says Brazier. \u201cThis can be very useful: often the lower water levels are used by baby beavers to practice swimming, away from outside dangers.\u201d<\/p>\n

Are beavers nocturnal?<\/strong><\/h2>\n

Yes, beavers are nocturnal. This probably explains why you haven\u2019t seen any during your riverside treks.<\/p>\n

\u201cNormally, they only actually leave their lodge to start grooming and feeding at about 7:00pm in the evening. They\u2019ll then find more food, mark their scent and check their territory\u2019s boundaries for the next 12 hours,\u201d says Brazier. \u201cAt around seven in the morning, they\u2019ll go inside the lodge to eat and sleep.\u201d<\/p>\n

So, why are beavers nocturnal? Like most night-time animals, this behaviour helps them avoid predators. However, with most of their predators now extinct in the UK, resident beavers are only truly nocturnal out of habit.<\/p>\n

\u201cThis means UK beavers could potentially evolve into daylight animals, but these changes will take a long long<\/em> time,\u201d Brazier says. \u201cRemember: they are creatures who have been evolving for millions and millions of years and they\u2019re likely to have been nocturnal animals for that entire time.\u201d<\/p>\n

Why do beavers slap their tails on the water?<\/strong><\/h2>\n

Wild beavers slap their tails because they feel threatened. No, they\u2019re not just showing off. Or trying to splash you.<\/p>\n

Just like how a rabbit thumps against the ground to warn its burrow, a beaver will slap the water with its tail to alert others before diving under. Any family member to hear the splash will likely return to the water too.<\/p>\n

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A beaver splashing its tail. Photo by Getty<\/span><\/figcaption><\/div>\n

\u201cThis is why if you\u2019re lucky enough to see any signs of beavers \u2013 think chewed timber \u2013 you should be very<\/em> quiet and move very<\/em> slowly,\u201d says Brazier.<\/p>\n

\u201cIf you can see a water line, keep your eyes peeled and look for big ripples. And be patient \u2013 it really will be worth it!\u201d<\/p>\n

Do you have any other great beaver facts?<\/strong><\/h2>\n

Glad you asked. Over time, beavers have evolved to have a handy comb on their back foot. On their right side, one of their claws has a cleft or split in the middle, which comes especially useful when grooming.<\/p>\n

\u201cThis inbuilt comb is an easy way of keeping a beaver\u2019s fur clean. And it\u2019s not just a matter of hygiene: dirty fur is actually one of the biggest killers of beavers. That\u2019s simply because clean fur is waterproof and warm,\u201d explains Brazier.<\/p>\n

Just remember: although it works for beavers, we absolutely cannot recommend growing your nails in the same way. Just think of what your mum would say about it.<\/p>\n

About our expert<\/strong><\/h4>\n

Richard Brazier is a professor of physical geography at the University of Exeter. Among other areas, he studies the reintroduction of Beavers in the southwest of England, particularly how the animals modify the landscape. His work has been published in journals including the Journal of Applied Ecology<\/em>, Restoration Ecology<\/em> and <\/em>Ecological Solutions And Evidence<\/em>.<\/em><\/p>\n

Read more:<\/strong><\/p>\n