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Why do beavers build dams? Nature’s engineers can help us protect the environment


Humans are not the only species on Earth that use technology to manipulate their surroundings and build impressive structures. Beavers, the second largest rodents on our planet, are also endowed with engineering abilities. They are capable of building dams that can last for decades or even more. Also, unlike most human-made structures that cause deforestation and loss of biodiversity, building beaver dams increases species richness, reduces soil erosion, prevents flooding, improves water quality, and of course, gives furry beavers a cozy home.

But why do they do it?

A beaver rests in the water. Image Credits: hansbenn/Pixabay

The most important benefit of beaver dams is that they promote the development of natural wetlands. According to a UN report, the survival of almost 40% of all species (including many endangered organisms) on Earth depends on wetlands. As such, beavers play a key role in improving and maintaining the health of many ecosystems.

Because they can make changes to the natural environment with their construction skills, they are also called ecosystem engineers. Their dams can even help filter pollution, and there’s no doubt that beavers’ impact on the environment is significant—and usually positive.

Why do beavers build dams?

Common beaver predators such as coyotes, bears, bobcats, foxes, wolverines, and humans can easily catch beavers on land, but in water, beavers can quickly outmaneuver them with their webbed toes, which are much better suited for swimming than walking.

Therefore, in order not to reach predators, beavers build dams over flowing water. These dams divide the body of water and lead to the formation of deep ponds over which the beavers build their homes, called dens.

Beaver lodge in open water in Canada. Image credits: Bridesmil / Wiki Commons.

Fast flowing water can damage the lodges and make them wet, but beaver dams keep the lodges dry, warm and protected at all times by acting as a barrier. Dams restrict the flow of water and cause the water level rise behind them, promoting that beaver-friendly environment.

Huts are always built over deep lakes, ponds and streams, so that when the water begins to freeze in winter, their underwater entrances are not closed.

Moreover, a lodge with an underwater entrance cannot be easily compromised by a terrestrial predator and can also be used as a quick escape tunnel in emergency situations. Thus, dams improve not only the comfort, but also the safety of the houses.

Beaver Dam located in Lassen Volcanic National Park, California. Image Credits: Walter Siegmund/Wikimedia Commons

Beavers don’t always make dams. If they cannot find a stream suitable for building a dam, they make houses and burrows on the ground and live there.

How are beaver dams built?

Beavers may not have access to the advanced tools and machinery we use, but they are blessed with strong jaws and ever-growing incisors. In addition, a single beaver can carry its own weight, which makes the animals excellent for this task. These impressive physical features allow them to build dams and lodges that will last for many years. For example, the largest beaver dam, found in Wood Buffalo National Park, Alberta, Canada, is believed to have been built in the 1970s. This glorious beaver dam is about 2,780 feet (850 meters) long, and researchers believe it has been used and maintained by many generations of beavers.

However, not every beaver dam is this big; in fact, they are usually three to five feet tall and 300 feet long. The construction of a beaver dam begins with beavers gnawing trees and thick branches located near the shore of a river or lake. Trees and branches become weak, fall into the pond and block the flow of water, several fallen wooden logs and branches stack together to form a strong foundation for the dam.

The largest beaver dam seen from a helicopter. Image credits: Parks Canada.

The beavers then begin adding dirt, rocks, grass, twigs, leaves, and small plants over and around the base to further expand the structure and make it more durable. Once the water level on one side of the dam is deep enough to form a winter entrance to the lodge, the beavers begin building lodges inside the dam building with chambers for nesting and eating. Beavers rest, store food, mate and raise their young in lodges, usually one beaver family (5 to 10 members) owns a particular dam or lodge, and when another beaver family tries to claim the home, they don’t hesitate to fight with intruders.

The importance of beaver dams to our ecosystem

Unfortunately, by 2015 our planet had already lost 35% of its wetlands, and as the rest of the wetlands are rapidly disappearing, 25% of swamp species are currently endangered. But beavers can help.

The deep ponds created by the construction of beaver dams not only provide beavers with shelter from predators, but also promote the growth of swamps, special water-rich ecosystems that support the growth of fish, birds, frogs, otters, and a host of other endangered flora and fauna. Wetlands are carbon-rich ecosystems that also play an important role role in climate regulation around the world.

Recent studies have consistently shown that beavers can play a role in preservation of the ecosystemand the positive impact of their dams far exceeds the costs. In the UK, beavers did unlikely to reoccur and now they are included in the wildlife restoration and conservation.

Image Credits: Nimpus/pixabay

By restricting the flow of water to create a reservoir, beaver dams prevent soil erosion and flooding and increase the water content of the soil, this increased water content leads to the formation of new wetlands.

In addition, beaver dams also prevent toxic chemicals from seeping deep into the earth and oceans. acts as a water filter and sediment traps. By creating these dams, beavers play a very important role in managing our ecosystem and therefore they are considered a keystone species. An experiment conducted in 2016 showed that building beaver dams in a habitat increases its natural complexity and caused improvement in endangered fish populations Oncorhynchus mykizha (also known as rainbow trout or steelhead).

A 2018 case study highlights that changing beaver habitat affects the composition of the benthos in the river and leads to growth new invertebrate organisms in the beaver pond, which are known to thrive in deep water. Interestingly, even after the beavers leave their altered habitat, the pond created by the construction of the beaver dam continues to support biodiversity in the region.

Another study published in November 2020 shows that beaver dams improve groundwater, promote microbial respiration, promote the growth of lotic and lentic species, positively affect the biogeochemical cycle that occurs in nature, provide stability against drought and increase food production. A a recent study from the National Resources Research Institute (NRRI) also shows that beaver dams can improve the availability of fresh water and make a significant contribution to the conservation of wetland ecosystems.

Conflict between beavers and humans

Flooding caused by beaver dams can damage farmland and adversely affect local crop production. In addition, the increased concentration of water in the soil due to beaver ponds can threaten the foundations of man-made structures such as roads, buildings, overpasses, etc. Moreover, in addition to cutting down riparian vegetation, beavers sometimes also gnaw large trees and plants. , which then end up on roads and trails, creating a danger to people’s lives.

A tree gnawed by beavers. Image Credits: fietzfotos/Pixabay

All such events sometimes lead to human abuse of these innocent creatures. However, there are many agencies, non-profits and environmentally conscious organizations working together to inform people about non-lethal and environmentally friendly methods of dealing with beaver-related problems.

There was a time when the beaver population in North America was around 200 million, but then in the 1800s, increased demand for beaver fur to make caste hats nearly drove them to extinction. Thanks to continued conservation efforts, the beaver population in North America has rebounded to 10-15 million. They are not currently endangered, but continuous exploitation of freshwater bodies and rapid urbanization are affecting many beaver families around the world.

Therefore, it is critical that we make environmentally responsible decisions when it comes to using development strategies so that both beavers and our ecosystem continue to thrive.

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