Beavers are the second-largest rodents on the planet, surpassed only by the Capybara. The size of this semi-aquatic mammal is best described using a combination of measurements: total length, average weight, and height at the shoulder.
Defining Beaver Dimensions
The average adult beaver has a substantial body mass, typically weighing between 16 and 30 kilograms (35 to 66 pounds). Individuals can occasionally exceed this range, with the largest specimens recorded reaching weights of up to 50 kilograms (110 pounds). This impressive bulk is necessary for their demanding lifestyle, which involves felling trees and constructing large dams.
The total length of a beaver, measured from the tip of the head to the end of the tail, generally falls between 95 and 125 centimeters (37 to 49 inches). This measurement includes the distinctive tail, which contributes significantly to the overall length. The body itself, from head to rump, typically measures about 74 to 90 centimeters (29 to 35 inches).
When standing on all fours, the height at the shoulder is relatively short, usually ranging from 36 to 43 centimeters (14 to 17 inches). This low-to-the-ground posture aids in their aquatic movements and provides the leverage needed for their powerful engineering work.
Size Differences Between Beaver Species
The size range encompasses the two existing species: the North American Beaver (Castor canadensis) and the Eurasian Beaver (Castor fiber). While both species are physically very similar, subtle size variations exist. The North American Beaver is generally considered the largest rodent in North America, with a typical adult weight range of 11 to 32 kilograms (24 to 71 pounds).
The Eurasian Beaver often has a slightly larger average body mass, with adults typically weighing between 13 and 35 kilograms. However, the North American species holds the record for the maximum known size, with occasional individuals surpassing the heaviest Eurasian specimens. Eurasian beavers also tend to have a slightly more elongated skull and a narrower tail shape.
Physical Adaptations and Structure
A significant portion of the beaver’s overall mass and physical structure is directly linked to its semi-aquatic lifestyle and engineering abilities. The large, paddle-shaped tail, a defining feature, is not fully furred and is covered in scaly, leathery skin. This tail can measure up to 45 centimeters (18 inches) long and 13 centimeters (5 inches) wide, serving as a rudder while swimming and a prop for balance while cutting wood.
The beaver’s stout body is heavily muscled, allowing it to pull heavy loads and withstand the cold of its aquatic environment. Their dense, waterproof fur also contributes to their substantial bulk, providing insulation. Structural strength is concentrated in the continuously growing incisor teeth, which are robust and orange-colored due to a high iron content in the enamel. This iron-reinforced structure enables the animal to fell trees efficiently, a behavior that defines its ecological role.