Is a Frog a Mammal? Differences & Facts
By Kit Copson
Updated on
In the world of vertebrates (animals with backbones), there are five main groups, which are mammals, reptiles, birds, fish, and amphibians. It can sometimes be tricky knowing which animals fall into each group. In the case of frogs, though, they are amphibians.
In this post, we’ll explain what an amphibious animal is and share the main differences between the animal groups.
Click to Skip Ahead:
- What Is an Amphibian?
- What’s the Difference Between Amphibians & Mammals?
- What’s the Difference Between Amphibians & Reptiles?
What Is an Amphibian?
The word “amphibian” is derived from the Greek word “amphibious”. There are two meanings within this one word—”amphi”, meaning “both” or “dual”, and “bios”, which means “life”.
In a nutshell, an amphibian is a cold-blooded vertebrate that typically spends the majority of its time as an adult on land (though not in every case—see below), preferring damp, moist environments. However, an amphibian’s eggs are typically laid in water, where its larval (tadpole) stage is also spent.
The larval stage of an amphibian’s life can last for up to 2 years in some cases, though it can be much shorter, sometimes lasting just a couple of weeks. In the tadpole phase, amphibians have gills, and some aquatic amphibians keep these as adults. The lungs and legs are developed during the growth phase (metamorphosis), and the amphibian can later use these to survive on land.
In short, many amphibians spend part of their lives in water and part of their lives on land, but some amphibians are largely aquatic for their entire lives whereas some live mostly on land—it varies. For example, bullfrogs are largely aquatic, whereas tree frogs spend most of their time on land.
Their skin has to be kept moist to allow them to breathe through the skin, which most amphibians can do in addition to breathing through their lungs. Animals in the amphibian group are frogs, toads, newts, salamanders, and caecilians.
Life Cycle of a Frog
- Egg: Frogs are not mammals because most mammals do not lay eggs (the duck-billed platypus and echidna are exceptions).
- Tadpole:Tadpoles begin to swim at around 7–10 days and are social by week 4.
- Tadpole with legs:Legs begin to develop between weeks 6 and 9, the tail is still long at this point.
- Froglet: A froglet is like a miniature version of an adult frog and has a stub instead of a long tail.
- Frog: This is the fully developed adult frog.
What’s the Difference Between Amphibians & Mammals?
One of the main differences between amphibians and mammals is that amphibians are born externally (via eggs), whereas mammals give birth to their young, and female mammals feed their young with milk while amphibians do not.
In addition, mammals are warm-blooded and amphibians are cold-blooded, and mammals have hair or fur (though some, like whales and elephants, have hair but less of it than many other mammals). By contrast, amphibians do not have hair or fur and instead have moist skin. Amphibians can breathe through both their lungs and skin, whereas mammals breathe through their lungs.
What’s the Difference Between Amphibians & Reptiles?
As with mammals, there are a few clear differences between amphibians and reptiles. For one thing, while amphibians have moist skin that shouldn’t be allowed to dry out, reptiles have dry, scaly skin adapted for life in hot, arid climates. While amphibians breathe through their skin and lungs, reptiles only breathe through their lungs.
Furthermore, though both amphibians and reptiles lay eggs, reptile hatchlings hatch more readily formed, whereas amphibian hatchlings go through a larval stage, typically in the water. For example, a frog starts out as a tadpole that gradually develops legs and lungs until it becomes an adult.
Final Thoughts
To recap, frogs are not mammals, they are amphibians, along with toads, newts, salamanders, and caecilians. They hatch from eggs as tadpoles that grow legs and lungs in the water to prepare them for an adult life spent mostly on land. Nevertheless, some frog species, like the African Dwarf Frog and the Titicaca Water Frog spend much of their lives in water.
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Featured Image Credit: yusuf kurnia, Shutterstock
