Four Main Stages in a Frog's Life Cycle

Depending on who you ask, a frog can have as few as three or as many as seven stages in their life cycle. That's because some sources will include only the stages of frog eggs, tadpoles, and adult frogs while others will include tadpoles with front legs, tadpoles with hind legs, and froglets in their description of the life cycle of a frog. The four main stages of a frog's life are generally held to be eggs, tadpole, froglet, and adulthood.

Adult American bullfrog (Lithobates catesbeianus) jumping in a forest lake
Four Main Stages in a Frog's Life Cycle
credit: ivkuzmin/iStock/GettyImages

Stage one: frog eggs

Depending on the species of frog, the mother can lay a handful or as many as 20,000 eggs at a time according to Reference.com. While the eggs are usually laid in or near water, a few in the rainforest lay their eggs in the trees so the embryos will drop into the water as they hatch.

After the mother lays her clump of eggs, the father will release sperm on the eggs to fertilize them.

Stage two: tadpole or polliwog

There is no real difference between a tadpole and a polliwog; they are just two different names for a newly hatched frog. These baby frogs look more like fish than they do adult frogs as they have no legs and are just heads </ahref="https:>with long tails when they first emerge from the egg, usually one-to-three weeks after the eggs are laid according to Thought Co. The tadpoles live more like fish than adult frogs since they have gills that allow them to breathe underwater and they spend their days eating plants and algae in the water.

There are three life stages of a tadpole. The first stage is where the creature has no limbs and only breathes with gills. During the second stage, the tadpole begins to develop lungs and has grown hind legs that allow it to hop around — this all happens in only about 24 hours according to Earth Rangers. During the third stage, the tadpole grows front legs, but it still has its long tail, which defines it as a tadpole.

Stage three: froglet

When the frog's legs have fully grown in, the tail will start to grow shorter and shorter until it is gone. At this stage, it is called either a young frog or a froglet and the animal will stay in the water, but will no longer eat because it gets all the nutrients it needs by absorbing its tail.

There are also changes inside of the frog, as well. Skin will begin to grow over the frog's gills. The tadpoles teeth that were used to rip up plants will disappear, and tongue muscles will develop to allow the frog to catch insects. The tadpole's large intestine, which was once used to digest algae and plants will shrink to better suit its meat-based diet. When the tail is completely gone, the small frog will hop out of the water for the first time.

Stage four: adult frog

Once the frog leaves the body of water, it is an adult frog. It will breathe exclusively with its lungs and begin to eat insects instead of plants. Frog lifespans vary based on the species, but they usually spend a few years growing to their full size before laying more eggs and beginning the cycle again.

The exceptions to the rule

It's said there is an exception to every rule and researcher Jim McGuire says there are around a dozen species of frogs that reproduce in a drastically different manner than most by taking part in internal fertilization. These frogs give live birth, mostly to froglets, although one species gives birth to tadpoles.