Four Main Stages in a Frog's Life Cycle

Updated November 21, 2016

A frog's life is a fascinating example of amphibian metamorphosis. Most frogs take only 12 to 16 weeks to reach maturity during the four main stages in a frog's life cycle. The traditional frog life cycle follows distinct steps that take it from an animal that can breathe underwater and survive on plant matter to a air-breathing insect-eater.


A female frog lays up to 5,000 eggs in a large mass in a pond or another wet place. The eggs, which are covered in jelly, are called frog spawn. Most of the time the females will leave the eggs, but a few species stay to protect the frog spawn. Bugs, fish and ducks all prey on the fertilised eggs. As the egg matures, the baby tadpole can be seen inside. It survives by ingesting the yolk inside the egg and grows gills and organs. After 21 days, the eggs will hatch and tadpoles will emerge.


The tadpole looks more like a small fish than a frog. The gills allow it to breathe in water. Right after hatching, the amphibian will stick to grasses or weeds in the water. After seven to 10 days, it will start to swim around while eating algae. Many gradual changes take place as it grows bigger. After four weeks, skin starts to grow over the gills. Tiny teeth start to form and the back legs sprout. Around this time, tadpoles become more social and start to school together. Around seven weeks, a tadpole's back legs are fully formed and bumps appear where the front legs will emerge.


At nine weeks, the amphibian will look more like a frog with a tail than a tadpole. This is the froglet stage. The body will elongate and thicken, and the head becomes more distinct. The froglet will start to eat larger items, including plants and dead insects. At 12 weeks the froglet only has a tiny tail stub. Once it reaches a certain size, a metamorphosis will suddenly take place. In the space of a day or two, the tail shrinks, the legs grow longer and the gills stop working. The developing lungs start functioning and the frog will drown if it does not leave the water.


The fully grown frog will now start the process again by looking for a mate. While doing this, the frog will feed on insects and worms. It will no longer eat plants. During the winter season, a frog will hibernate by purposely dropping its body temperature and storing up glucose for fuel. When spring comes, the frog will "thaw out" by raising its body temperature and prepare to breed. Frogs will migrate to breeding grounds, mate and produce fertilised eggs, starting the cycle again.

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