Turtles are reptiles, not mammals. Reptiles are a group of cold-blooded animals that are distinguished by their dry scaly skin and their ability to breathe air. They are considered “cold blooded” because they are unable to control or regulate their own body temperature, so must rely on external sources for heat.
This is in contrast to the mammals, which are warm-blooded. Warm-blooded animals are able to maintain a constant body temperature, and are therefore are not dependent on external sources of heat.
The name “Mammal” comes from the Latin word for breast (“mamma”). In females of all mammal species, milk are produced and secreted into mammary glands. Mammals are characterized by having four limbs instead of just one or two as seen with reptiles. The skin covering most mammalian bodies are covered with hair/fur while most reptile are covered with scales. This body covering makes it easier for mammals to retain heat since they are able to hide inside fur or flee quickly under their own cover unlike a turtle, who must rely on external sources of warmth and protection.
Another major difference between are turtles are mammals and are reptiles is the way they are born. As a reptile, most are hatched from eggs while mammals are born live.
Mammals are also typically are larger than reptiles in terms of overall mass. Because of this, there are specific adaptations that allow mammals to carry their young. This includes specialized processes in birth, such as delayed gastrulation (live birth) which prevents the animal from emerging until it is fully developed, or lactation among females that allows them to feed offspring with milk produced by mammary glands for various lengths of times after birth. The emergence of features such as these have allowed biologists to determine whether an organism is a mammal or not based upon its physical structure alone rather than simply relying on the presence of fur or scaly skin.
Key points:
- Turtles are reptiles, not mammals
- Reptiles are cold blooded, mammals are warm-blooded
- Warm blooded animals are able to regulate their own body temperatures
- Reptiles are dependent on external sources of heat
- Mammals are larger than reptiles in terms of overall mass
- Mammals are fur covered while reptiles are mostly scaly
- Mammals are born live, most reptiles are hatched from eggs
Turtles are never mammals because they do not possess any of the characteristics associated with an animal that is able to regulate its temperature without external sources of warmth, are larger than a reptile and can bear live young in the same manner as a mammal.

I have a big soft spot for turtles. I grew up near a pond that was full of snapping turtles. Now and then I’d see them crawling across our front yard, which was always exciting.
Now I write about turtles for this website as a fun side hobby. Glad you stopped by!