The American beaver is a semi-aquatic mammal native to Canada, including the Toronto area. While Toronto and Region Conservation Authority (TRCA) does not monitor beaver populations, they have been documented in every watershed within our jurisdiction.
Beavers eat mostly woody vegetation, including mature trees, and love to stop water from flowing. It is these situations that can potentially create conflict with people.
Beaver Ecology 101
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As the largest rodent in North America, the American beaver (Castor canadensis) is a strong and robust mammal. Adult beavers can weigh up 32 kg and measure up to 1.3 metres in length (tail included).
Beavers have evolved into super swimming machines. Their small nostrils close automatically when they become submerged in water, and their eyes have a third transparent membrane so that they can see underwater. The beaver uses oil glands to distribute oil throughout its brown coat, making it extremely waterproof.
The beaver’s webbed hind feet are ideal for swimming, while it uses its unwebbed front feet with great dexterity to grip and hold branches, mud and stones. Beavers also have long front incisor teeth, maintained chisel-sharp, that are capable of felling large trees. Their lips can close behind their teeth, enabling them to chew underwater.
DID YOU KNOW? The beaver’s front incisors never stop growing! Chewing trees wears down the teeth and prevents them from getting too long. Thick, iron-rich enamel makes their teeth orange in colour.
The beaver’s most distinguishable feature is the tail, which it can use to slap the water, warning other beavers of danger, and which also provides counterbalance when carrying heavy trees.
Beavers typically live in a family group, with a pair of monogamous adults, their yearlings, and young kits. They establish a territory that they mark with strategically-placed scent mounds to tell other beavers that this is their turf.
Within their territory, they may create a lodge located in the middle of a waterbody, or they may dig a burrow into a bank.
DID YOU KNOW? Beavers do not hibernate. Over summer and fall they create a food cache of woody plants, stored in water near their lodge, so that in winter they can swim out below the ice, chew off twigs, and return to the lodge to eat.
Beavers may also create dams by piling sticks, stones, and mud to slow the flow of water and make it deeper, providing a safe place for the lodge that will remain accessible during the winter (since the water does not freeze all the way to the bottom).
Beavers are herbivores, eating the bark and cambium of woody plants. They will also eat aquatic vegetation, grasses, grains, and even fallen apples.
Beavers are considered “ecosystem engineers”. They stop natural succession by removing trees and flooding areas. In doing so, beavers create wetland habitat for an array of other native wildlife, and actually increase the biodiversity of the area.
Beaver ponds and wetlands help recharge groundwater, and can help prevent catastrophic flooding by slowing, spreading, and storing stormwater. These ponds and wetlands are also beneficial during droughts, as the water stored in them is absorbed in the sub-surface, helping to increase stream flow in drought conditions.
Beaver dams can also help improve water quality by reducing erosion and retaining sediment, which helps to filter pollutants.
DID YOU KNOW? Beavers are mainly nocturnal? Most of their foraging, dam building, and lodge building activities happen at night. But you can still sometimes spot beavers in the daytime, especially at dawn or dusk.
Beavers in an Urban Landscape
While beavers enrich our natural environment, their behaviours can create problems in an urban landscape.
Beavers prefer slow-moving, low-gradient streams like those found within our urban areas. They also enjoy eating the trees and shrubs that are frequently planted along our watercourses. In addition, urban beavers have few natural predators, so their populations may be higher than expected in urban settings.
Humans put a high value on trees — especially in urbanized environments like the GTA, where tree cover is limited. So when people observe beavers felling trees, they become understandably concerned.
However, it’s important to remember that our native trees and shrubs and beavers have co-evolved together, and that many species — including the beaver’s favourites, willow and poplar — will regrow from the stump.
Similarly, when beavers flood forested areas, it can be difficult to tolerate the loss of mature trees. But keep in mind that this is a natural process, and that the death of trees creates opportunity for different habitats and wildlife. Standing dead trees, or snags, attract fungi and invertebrates as the wood decomposes, and in turn this attracts other wildlife due as the food web expands.
Snags and fallen logs also provide perching, nesting, roosting, and cover opportunities for a wide range of wildlife including birds, mammals, turtles, amphibians, and fish.
When should I be concerned about beaver tree removal?
Beavers seem to hate the sound of running water, and their damming activities can create concerns about flooding and downstream erosion in the event a large dam fails.
When should I be concerned about beaver-related flooding?
“Beavered” Trees: Should I Be Worried?
Sometimes beavers chew on trees near infrastructure — including near buildings, roadways, power lines, trails, and fences — as well as in areas people frequent, like parks and picnic areas. Partially chewed trees may need to be removed if they pose a hazard.
If you see a tree that is at risk of falling, causing damage to infrastructure or endangering human safety, please contact the infrastructure/property owner and/or municipality.
Beaver-Related Flooding: Should I Be Worried?
TRCA receives dozens of concerns regarding beavers each year. When beaver dams are located in areas with wide floodplains, they are typically of little concern.
However, dams located in developed areas with narrow floodplains can pose problems if there is not enough room for the beaver to create a pond without flooding out infrastructure, which can threaten buildings, roads, and trails.
It is the landowner’s responsibility to protect their own property from flooding, including any negative impacts caused by beavers. Find out what to do if a beaver dam is on your private property.
TRCA will only intervene if the dam is located on TRCA-owned property and poses a risk to infrastructure or property. If the beaver dam is located on public or municipally owned land, please call your local municipal general inquiries line to be directed to the appropriate department.
To report a beaver dam on TRCA-owned property please use our online form.
How TRCA Mitigates Beaver Activity
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METHODS
Selective Tree Wrapping
Selective tree wrapping is a successful method for protecting trees. Enclosing the base of the tree with a 36-plus-inches-tall utility fence will usually prevent beavers from accessing the tree.
This is best done selectively to protect specific trees (mature native species, rare native species, memorial, or other valued trees).
Care must be taken to allow ample space for tree growth, and wrapping must not be bound tightly to the tree.
Plantings to Provide an Alternative Food Source
Planting of native shrubs can provide a food source for beavers; shrubs provide a regenerative food source and can help to reduce tree loss.
Species such as red osier dogwood are regularly consumed by beavers and will typically regenerate rapidly after being chewed on by a beaver.
Dam Removal
Prior to dam removal, TRCA undertakes a risk assessment to determine the actual risk of flooding, erosion, and damage to infrastructure.
If the assessment indicates a risk, and the dam is located on TRCA property, action is initiated to address the risk.
Dam removal may involve repeated notching of a dam to allow for upstream stored water to be gradually lowered. This is done in a slow and methodical fashion to reduce the impacts of downstream erosion and the release of sediment.
The timing of dam removal is important.
Dam removal in late fall or winter could endanger overwintering beavers, as they typically rely on deep water to store and access food caches. Likewise, dam removal during the spring and early summer months could endanger young beaver kits.
Exclusion
Conventional fencing, with an additional base of wire mesh, can be used to prevent access to water or potential damming locations.
Culvert protectors reduce the ability of beavers to create severe culvert blockages.
Pond levelling systems may be used on existing dams to regulate the water level, reducing flooding upstream and fooling the beaver into thinking the dam does not allow water through.
Although this method can be effective, it limits fish passage and may not always be appropriate.
These devices are usually constructed from plastic or metal culverts, with the upstream end placed at the desired depth and perforated with several holes to allow water flow.