North American Beaver

(Castor canadensis)

The American Beaver is on the most part nocturnal (with some exceptions -- the individual in these photos happened to be active in the daytime).
More info coming soon.


Since Beavers are vulnerable to predators while on land, they tend to spend more of their time within the water. Dams provide a means of keeping watersheds deeper which in turn allows them to escape below the surface should danger be present. Although not an issue in Rocklin's climate, dams also serve to keep water deep enough so that it does not freeze solid in winter thus allowing the Beaver access inside their lodge. Branches (from trees the beavers cut down), reeds, rocks, grass, and mud are all used by the Beaver in constructing a dam.

Beaver Dam 11/25/2016 (view from southwest side)
Beaver Dam 3/11/2016 (view from west downstream)

Beaver dams contribute to the health of the ecosystem in many ways. Dams slow water flow and help reduce soil erosion . In the rainy season the waters within a Beaver dammed pond percolate down, raising the groundwater table. As the season changes to the hot dry months of summer these extra waters help to increase stream flow. Beaver ponds have also been shown to improve water quality by removing sediment and pollutants including total suspended solids, total nitrogen, phosphates, carbon and silicates. Fecal coliform and streptococci bacteria excreted into streams by grazing cattle can be reduced downstream by the slower water currents of the Beaver pond which allow the bateria to settle to the sediments at the bottom.

Dams & Effects of the Drought in CA

Today, interest in beavers in California is on the rise as the benefits to fish and wildlife habitat, surface water storage and ground water recharge become more apparent during drought conditions.
--- California Department of Fish and Wildlife,
During the summer of 2015 parts of the creek in our local Rocklin CA area dried up entirely leaving areas along the "wetlands" devoid of fish, frogs, turtles, etc. We observed that the few areas still containing some water during the months of July up until the first rain were the areas of water held back by the Beavers' dam. The following images show the effects of the drought on the water's path downstream where the Beaver dam was not present to retain water.
Creek on 8/4/2015
Creek on 9/13/2015

Here is how this same area looks on 8/3/2016 after a better year of rainfall history but by no means out of the drought. The deeper waters still lie upstream from this area above the Beavers' dam.


Beavers construct 3 types of lodges depending on the features of the habitat in which they live. Lodges are built on the banks of ponds, on islands, or on the shores of a lake. They may be surrounded by water or positioned beside land and can include burrows dug into the substrate of a bank. The lodge takes the form a domed oven-shaped hut and is constructed of sticks, twigs, grass, rocks and mud. The size of a lodge may increase over the years with repair & add-on building.
Lodges built in ponds are positioned either partly hanging over the water's edge or a short distance from the bank with the front wall built up from the bottom of the water. The beavers begin construction by building a pile of sticks and then eat out one or more underwater entrances with 2 platforms above the water's surface inside the pile. The first platform is used for drying off when emerging from the water. The room inside the lodge be up to 8 ft wide 3 ft high and the floor is lined with bark, grass, or wood chips. A small air hole is left in the top of the lodge for ventilation. The lodge is often plastered with mud which has a consistency of concrete when it freezes in cold weather.

Weight: 28.63 to 70.48 lbs.
Length: 35.43 to 46.06 inches.
Lifespan: 10 to 20 years in the wild.
Diet consists of
Can be found from

Breeding Season: Once a year in late December to May (more often January or February).

Breeding Age: 3 years old (20% of females reproduce at 2 years of age).

Gestation : 128 days on average (3 months).

Litter Size: 1 to 6 kits. Kits are weaned at 2 weeks old.

Kits will live with parents for about 2 years.


  1. "American Beaver (Castor canadensis)". Taxa, All Species, Catalog of Life: 2012, Retrieved November, 2016.
  2. "North American Beaver". Wikipedia, The Free Encyclopedia. Retrieved November, 2016.
  3. Anderson, R. 2002. "Castor canadensis". Animal Diversity Web. Retrieved November, 2016.
  4. "Keep Me Wild: Beaver". California Department of Fish & Wildlife, Retrieved November, 2016.