Why Are Beavers Mammals?


There are two species of beaver in North America; the North American beaver and the mountain beaver. Somebody asked me if they were both species of mammals.

Beavers are mammals and have several mammalian traits. Beavers are vertebrates, they have mammary glands which they use to feed their live young, they have a four-chambered heart, have fur, and have sweat glands which they use to cool down.

If you want to find out more about the characteristics that beavers share with other mammals then please read on.

If you or someone you know loves beavers then have a look at my favorite beaver gifts on Amazon.

Is A Beaver A Vertebrate?

One of the characteristics that all mammals have is that they have a backbone inside their body. However, it is not just mammals that have a backbone.

Other animals such as fish, amphibians, reptiles, and birds also have a backbone. Animals with a backbone are called vertebrates.

There is another group of animals called invertebrates. These are animals that don’t have a backbone inside their body. Some examples of these include single-celled organisms, earthworms, starfish, octopus, snails, clams, insects, and spiders.

Beavers are classed as vertebrates as they do have a backbone inside their bodies. The spinal cord is surrounded by cartilage or bone.

Does A Beaver Have Mammary Glands?

Another characteristic that mammals have is mammary glands. The name mammal is taken from the Latin word mamma, which means breast and was popularised by Carl Linnaeus, a Swedish botanist, and zoologist.

Mammary glands are used to produce milk to feed the young after birth. Milk is produced in the mammary gland after childbirth and is called lactation.  

Beavers produce milk within their mammary glands. Beavers have four nipples which are only visible when the female is lactating. This is one of the only ways to tell the difference between male and female beavers.

Beavers usually give birth to between one and six kits. Beavers are fully weaned off milk from their mother at about six weeks. The milk contains essential nutrients for beavers in the early stages for them to grow healthy.  

Beaver couple

Does A Beaver Have A Four Chambered Heart?

Mammals all share another characteristic, one which is also shared with birds. Both birds and mammals have a heart that contains four chambers. Surprisingly, crocodiles, which are a reptile, also have a four-chambered heart.

The four-chambered heart is essential for the respiratory system of mammals. When mammals breathe in air, they take in oxygen. Oxygen is needed to survive but the waste product once the oxygen has performed its function is carbon dioxide. Carbon dioxide is expelled back into the air when we breathe out.

The respiratory system allows us to breathe in oxygen and breathe out carbon dioxide. Oxygen enters the lungs where the cells of the body transport it through the blood to the left ventricle of the heart. The left ventricle pumps oxygen-rich blood to the left atrium. It is then pumped through your arteries to the rest of your body. 

The other two chambers of the heart are the right atria and right ventricle. Oxygen-poor blood is received from the veins and is pumped to the lungs where the carbon dioxide is expelled.

The four-chambered heart which mammals possess is essential. A four-chambered heart is essential for warm-blooded animals as they expend a lot of energy and require a lot of oxygen. The four-chambered heart is an efficient way of getting lots of oxygen into the body.

Beavers do have a four-chambered heart. Beavers need plenty of oxygen as it is needed to burn sugars and fatty acids in their cells to produce energy. The energy is needed for everything they do including keeping themselves at a steady temperature.

Do Beavers Have Hair?

Another characteristic of a mammal is that they have hair or fur. The fur is generally used when a mammal has very thick body hair. Humans have hair, but we wouldn’t generally call it fur, whereas other mammals which are covered, such as bears or raccoons would have fur.

Hair or fur consists of two layers. These consist of a thicker underfur covered with oily guard hairs on top.  

The guard hairs are longer and coarser. They are used to repel water from the skin and to block ultraviolet rays from the sun. In animals that have markings, such as a jaguar, these markings are on the guard hair layer.

The thick underfur, or down fur, is used to keep the animal warm and is made up of curly or wavy hairs.

Even whales and dolphins have hair, although some species only have hair follicles. Species such as the humpback whale have hair their entire life with a single hair coming out of each hair follicle.  

Toothed whales usually lose their hair shortly after birth.

As anyone who has seen a beaver will know, they do have a coat of fur. The hair on a beaver is also known as fur and beavers have been hunted for their fur.

North American beavers have thick, waterproof fur which keeps them dry and warm.

Do Beavers Have Sweat Glands?

Mammals need to regulate their temperatures, and although all mammals sweat, not all cool down in the same way.

For us, sweating is a way of regulating our body temperature so that we don’t overheat. The sweat glands produce sweat which is then carried away from the body by evaporation. This carries away the heat and makes us feel cooler.  

Humans aren’t the only mammals that sweat through their skin. Primates and horses also sweat through sweat glands.

Some other animals use different ways to expel heat from their bodies. These can include panting, which is something you see in dogs when they have been out playing. This allows them to get rid of heat through their mouth

Most mammals do not have sweat glands on their bodies in the same way we do and need to use these other ways to cool down.

Beavers are one of the strangest mammals in regards to sweating as they do sweat, but not in the way that we do. Beavers do have sweat glands on their bodies, but as their fur covers most of them, they do not provide an adequate way to cool down. 

Beavers have sweat glands on their paws and sweat using these.

Do Beavers Have A Neocortex?

The brain is one of the most complex organs in a mammals body. There are many areas in the brain.  

The cerebral cortex is the outer layer of the brain and is used for functions such as movement, processing information from the five senses, decision making, and in humans, speech. 

The neocortex is a set of layers of the cerebral cortex and it is this part of the brain that controls sensory perception, motor commands, spatial reasoning, and conscious thought.

The neocortex also allows mammals to store memories, including experiences and events.  

The larger the neocortex, the larger the capacity to control conscious thought, spatial reasoning, motor commands, and sensory perception.

The majority of brain cells are found in the neocortex and the cerebellum. The cerebellum is used for posture, coordination, and balance.

The neocortex looks different in different animals. Humans, primates, and other larger animals have grooves (sulci) and ridges (gyri) and the brain is similar to what you may have seen before. The grooves, ridges, and folds allow a much larger neocortex to fit inside a smaller space.

Small mammals such as rodents do not have the deep grooves and ridges and the neocortex is much smoother. This shows that their brains are much smaller in comparison.

A 17kg beaver has a brain that weighs about 45g, and its intelligence is thought to be between rodents of its size and squirrels.

Beavers do have a neocortex but there are fewer folds and therefore a smaller neocortex relative to their brain size.  The size of the brain however is no different from a non aquatic mammal.

Do Beavers Have Three Middle Ear Bones?

Another trait that mammals possess is three bones in the middle ear. These three small bones are called ossicles and conduct vibrations (sound) to the inner ear from the eardrum.

The three bones are called the malleus (hammer), the incus (anvil), and the stapes (stirrup).

Once the vibrations are in the inner ear, the vibrations are converted into nerve impulses. These three bones play a vital role in a mammal’s ability to hear.

With many animals relying on their sense of hearing to be able to hear prey and predators, this evolutionary trait is essential for mammals to survive.

Beavers do have the three small inner ear bones which help them to hear. Beavers have had these three earbones for many millions of years as fossils from the Pleistocene beavers also had these bones.

Beavers have a good sense of hearing, which we know as they react to tail slaps from other beavers. Females slapping their tails makes beavers move to deeper water for example.

However I have not been able to find put any proof of how good a beavers hearing is.

If you or someone you know loves beavers then have a look at my favorite beaver gifts on Amazon.

Bryan Harding

Bryan has spent his whole life around animals. While loving all animals, Bryan is especially fond of mammals and has studied and worked with them around the world. Not only does Bryan share his knowledge and experience with our readers, but he also serves as owner, editor, and publisher of North American Mammals.

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