Otters and beavers are two common semi-aquatic mammals that can occur in the same habitats.
When seeing them from afar, it can be challenging to tell the difference between the two. However, these differences are crucial.
Beavers are semi-aquatic herbivores that chomp off trees and build water dens and dams. They are a social, non-aggressive species with an appearance similar to groundhogs. Otters have rounder faces and generally lighter colors. They are an aggressive, solitary species feeding on fish and small mammals. Otters don’t build dams, but they can occupy abandoned beaver dens.
The table below shows a quick list of facts and comparisons between otters and beavers*:
| Characteristics | Otters | Beavers |
|---|---|---|
| Classification (family) | Mustelidae | Castoridae |
| Appearance | Various shades of brown with a darker back and lighter underside. | Gray to reddish-brown fur, lighter on the underside but more uniform in color than otters. |
| Skull & teeth | Circular, furry faces with short noses. Long and sharp canine teeth. | Large skull with a narrower muzzle. Disproportionately large incisors. |
| Length | 2 to 6 feet long | 2 to 3.25 feet long |
| Shoulder height | Approx. 12 inches | 8 to 9 inches |
| Weight | 10 to 90 pounds | 35 to 65 pounds |
| Bite force | 615 PSI | 1,073 PSI |
| Speed (in water) | 6 mph | 4 mph |
| Diet | Carnivore | Vegetarian |
| Behavior | Solitary | Social |
| Reproduction | Polygamous | Monogamous |
| Habitat | Rivers and seas | Rivers and lakes |
| Geographic range | North & South America, Europe, Asia, Africa | North America, Europe, Asia |
*Data in the table above was sourced from scientific publications, research papers, and other official sources cited throughout the article. The information included refers to averages for otters and beavers in general. Actual facts can vary from one subspecies to another.
Topics
Otters Vs. Beavers: 12 Key Differences And Similarities
1. Classification
To the untrained eye, otters and beavers may look alike. However, the only biological similarity between the two is that they are both mammals.
Otters are carnivores and belong to the mustelid family, the same as badgers, ferrets, wolverines, and weasels.
Beavers are rodents and belong to the family of castors. They are more related to gophers, kangaroo rats, and pocket mice than otters.
2. Appearance
A similarity between otters and beavers is that they are both semi-aquatic mammals. Both species have stockier bodies, webbed feet, and flat tails that aid during swimming. However, the similarities end here.
Otters are generally pale to darker brown in color with a brownish-white throat and chin. The shape of their bodies is similar to that of other mustelids, and the tails are thick, tapering, and covered with short hairs.
Beavers have a more yellowish- or reddish-brown coat. The fur on the neck and chin is also lighter in color, but the color difference is minimal compared to the back fur. In otters, the color difference is much more visible.
A beaver’s tail can also vary in shape and length, from short and broad to narrow and long. However, it is generally hairless and covered with black scales. From a distance, beavers look similar to groundhogs.
3. Skull & Teeth
One of the main traits to notice in beavers is the disproportionate skull size compared to the rest of the body.
These mammals have large heads with a narrower muzzle that is similar to that of other rodents. The dental formula and tooth shape also makes it clear that beavers are rodents.
Beavers have 20 teeth, the largest and most prominent of which are the two front incisors. They don’t have any canines and only have two premolars. In fact, the dental formula for hemimaxilla is I.C.PM.M – 1.0.1.3.
Otters are carnivores, and their dental formula and tooth shape reflects this fact. The dental formula of otters is similar to other carnivores. They have an I.C.PM.M for the hemimaxilla of 3.1.4.1.
Similar to other carnivores, such as coyotes, they have another set of molars on the lower jaw (3.1.4.2).
Otters also have rounder skulls with flatter and rounder noses, large eyes, and eye sockets placed higher on the skull.
4. Size
Adult otters generally measure between two and six feet in length, reaching heights of about 12 inches at the shoulder.
Beavers typically measure between two and just over three feet in length, their shoulder height ranging between eight and nine inches.
However, that’s not to say that otters are actually bigger than beavers.
While giant otters are definitely larger, most river otters (that live in the same habitats as beavers) can actually appear smaller. That’s because beavers typically have hunched backs that can reach heights of 12 inches or over.
Beavers also have stockier bodies than otters, making them look larger overall.
The video below highlights the minimal size differences between river otters and beavers:
5. Weight
The stockier bodies beavers have can give them an advantage as far as body mass is concerned.
They usually weigh between 35 and 65 pounds, the males generally being larger and heavier than females.
Considering all otter species, these mammals can range in weight from 10 to 90 pounds. However, river otters are on the lighter side, typically weighing between 11 and 30 pounds.
6. Bite Force
Although most otter species don’t live in the same habitat as beavers, these rodents and river otters frequently share a territory.
The two species typically ignore each other, but who would be able to inflict greater damage in a fight? Apparently, the beavers.
In a study about the feeding efficiency of American beavers, researchers found that their incisor bite force can be as high as 1,073 PSI.
This isn’t exactly surprising, considering that beaver teeth and jaws are strong enough to cut off trees.
Otters might have a bite force much stronger than humans – and other carnivores, as a matter of fact – but they are almost two times weaker than beavers, only mustering 615 PSI.
7. Speed (In Water)
Another difference between otters and beavers is the swimming speed.
Otters can reach a speed of about six miles per hour in the water. Beavers are slower, generally swimming at speeds up to four miles per hour.
Perhaps the difference is explained by the fact that beavers spend most of their time in the water swimming leisurely around or relaxing. They do most of their foraging on the ground.
Otters feed mostly on fish. Hence, their speed is crucial for pursuing and catching their prey.
8. Diet
One of the biggest differences between beavers and otters is their diet.
Otters are carnivores, and their diets mostly consist of aquatic animals. These small mammals are apex predators in their habitat, enjoying carps, trout, salmon, mussels, snails, crabs, crayfish, turtles, frogs, and a variety of other crustaceans, fish, and amphibians.
They also feed on waterfowl and eggs, and they can sometimes consume aquatic plants.
Beavers are primarily lignivorous, feeding on tree cambium and bark. They also eat leaves and other plant materials, including aquatic plants.
Fruits, such as apples, are also high on their preference list, and they also occasionally eat mushrooms.
9. Behavior
Describing the otter behavior can be challenging since each subspecies has its own peculiarities.
Referring to river otters, their behavior is aggressive and solitary. They are diurnal creatures with crepuscular peaks, meaning that they are more active at dawn and dusk.
However, river otters sleep at night and can be seen catching fish, swimming, or feeding throughout the day.
River otters are territorial and have large home ranges that reach 48 miles of waterway.
Beavers are also territorial, but they are social animals living in colonies of up to eight related individuals. All family members share a den that they build themselves on a body of water, using tree trunks and sticks cut off with their teeth.
Beavers also build dams that slow down the stream and create a peaceful environment for them to live in.
Like otters, beavers are crepuscular. However, they are nocturnal and remain active throughout the night. At dusk and throughout the night, individuals travel great distances in search of food.
Neither otters nor beavers hibernate; however, beavers build food caches in the fall and remain inside their dens in the colder months, consuming food from the stash.
Otters don’t build food caches and have to catch fish all year round.
10. Reproduction
Another difference between river otters and beavers is the reproduction system.
Beavers are monogamous and generally mate for life. However, if one partner dies, the other may seek a new partner.
North American beavers breed once a year, their mating season peaking between January and February. The female gives birth to up to four kits after an average gestation period of 128 days.
River otters are polygamous, with males and females only associating during the breeding season, usually in late spring.
Females delay implantation and only give birth from November to May, after a gestation period of about 60 days.
11. Habitat
Both beavers and otters have similar habitats; these species live near bodies of water.
Beavers generally live near ponds, lakes, or rivers, regardless of their geographic range. Otters may be found near lakes, ponds, rivers, seas, or oceans, depending on the geographic range and subspecies.
12. Geographic Range
While both otters and beavers are widespread, otters have a larger geographic range. They are found on all continents, except for Antarctica and Australia.
Beavers are found in North America, Europe, and Asia.
Who Would Win A Fight?
While otters and beavers don’t bother each other normally, there could be clashes between them. Despite their stronger bite and minimal differences in size, beavers wouldn’t necessarily have the upper hand.
As carnivores, otters are aggressive and accustomed to killing. Their behavior alone would give them an advantage since beavers are easy to scare off. However, should the beaver fight back, it might fight off the otter.