You learned in school that there are certain characteristics that define a mammal. They are warm-blooded, give live birth instead of laying eggs, they have hair or fur, and they have a vertebrae backbone. You even remember that the young feed on milk delivered by the mother. However, there are some organisms out there that you may have a hard time believing that they are actually mammals. Let’s take a look at some of them.

Bats

Bats are one of those critters that you may think twice before realizing that it is a mammal. Perhaps it is because they fly. Perhaps it is because their wings are membranes of skin that don’t seem to fit into the world of mammals. However, when you think about it further, you realize that the rest of their body is covered with hair. Yes, all bats are mammals!

Dolphins and whales

In general, your mind may think that vertebrates that live their whole lives in the water are fishes. However, this is not the case for dolphins and whales. Perhaps you doubt their taxonomic status because you wonder how they could give live birth and feed their young in the water. You know that the adult must surface regularly to breathe so how could a baby be born underwater? Well, this is actually what happens. The baby surfaces just like an adult to take in oxygen. The babies are fed like any other mammal, by suckling on a teat of the mother. They simply do it underwater. Yes, all dolphins, whales, and even porpoises are mammals!

The Giraffe

A giraffe is a very tall, horse-like animal that for a moment may leave question in your mind. However, you see the smooth fur and the young taking milk from its mother. Perhaps the question of doubt lies in the neck. You may know that all mammals have seven bones in their neck. This makes sense for a human and a mouse, but it also is true for the giraffe. Their cervical vertebrae are simply much larger than each of ours. Yes, the giraffe is a mammal!

Armadillos

Okay, what about the odd-looking armadillo? Those critters must certainly be reptiles, closely related to a turtle. Well, no. The armadillo, although it has a rounded back that may resemble a furless shell, does have hairs around the body. Their backbone is under the protective covering that forms their back. They do give live birth, in fact always to quadruplets of the same sex! Yes, an armadillo is a mammal!

The Naked Mole Rat

If you have ever seen this small critter you probably wondered if it is even from this planet! However, these highly eusocial animals do fit the criteria for mammals. They have a few sparse hairs on their wrinkly pink bodies. They give live birth and care for their young by delivering milk to them. Yes, despite their unusual physique, naked mole rats are mammals!

The Duck-Billed Platypus

Okay, this critter certainly cannot be a mammal. Native to Australia this animal has the body of a fuzzy mammal, but the bill of a duck. It must be a rule-breaker. Well, in fact, it is. Duck-Billed Platypuses are Monotreme mammals. They, in addition to echidnas, actually lay eggs. They fulfill all of the other requirements, including delivering milk to their young, have fur, and have a backbone. However, their young hatch out of eggs. Regardless of this odd feature, these few Monotremes, like the Duck-Billed Platypus, are mammals. Perhaps you can think of them as the exception in the mammalian world!

Conclusion

The world of mammals is very diverse making the group very interesting. At times you may wonder if a certain animal is really a mammal or not. Remember to look for the characteristics of mammals, but then remember that at times, there are exceptions. Remember to utilize resources like books and the Internet to look up any animal you may wonder about as knowledge is priceless! Why wonder when you can know for sure?

Photo credit: Julie M. Ray