Frogs have a somewhat complicated childhood.
Their life cycle includes four main stages.
Throughout these stages, frogs undergo a serious makeover!
What’s perhaps most interesting about the frog life cycle is the way it mirrors the evolution of the first land-dwelling vertebrates.
Frogs resemble primitive fishes during the early stages of development.
Amphibian metamorphosis provides a great model to demonstrate how limbs may have evolved in early amphibians.
So, what is the life cycle of a frog?
In This Article
What You’ll Learn
In this article, you’ll learn everything you could possibly need to know about the frog life cycle, including:
- The egg phase
- The larval phase
- Metamorphosis (tadpole to frog)
- Adulthood and reproductive maturity
- …and we’ll summarize all of this info in a handy diagram!
We’ll also talk about the lives of tadpoles and their journey to adulthood in detail.
What Is the Life Cycle of a Frog?
Frogs have four main stages of life:
- Egg phase
- Larval (tadpole) phase
- Metamorphosis (tadpole to frog)
- Adulthood
In this section, we’ll run through each stage and describe the steps in detail.
Stage 1: Egg Phase
The first phase of a frog’s life is the egg phase.
Frog eggs (or frogspawn) differ from the eggs of birds or reptiles, as they have no solid outer shell.
Instead, they consist of a yolky center surrounded by a matrix of protein called albumen.
This layer protects the delicate embryo from harm, while the yolk provides nutrients for growth.
Female frogs can each lay up to 4,000 eggs! Most species lay their eggs in large clumps known as “egg masses.”
The chance of survival to adulthood is slim for young frogs – only around four percent.
By laying as many eggs as possible, mothers increase the chance that a few will survive to adulthood and pass on their genes.
Frogs lay their eggs in the Springtime (in temperate climates) or at the beginning of the wet season (in tropical climates).
For protection, frogs tend to lay their eggs in vegetation near the surface of the water.
The gelatinous albumen coating helps the eggs to stick to surfaces and stay put.
Some species even make “nests” out of bubbles!
The eggs remain stuck in place for one to three weeks as the embryos mature.
Before leaving the egg, they need to develop internal organs, gills, and a strong tail to prepare them for their next phase of life!
Fun Fact: Frogs are cold-blooded (or ectothermic), so the time taken to develop is mainly dependent on temperature.
Stage 2: Larval Phase
The larval phase begins from the moment young frogs emerge from the egg. Frog larvae are more commonly known as tadpoles .
All tadpoles are fully aquatic, meaning that they live in water.
They lack lungs to breathe air and possess simple gills instead. Their paddle-shaped tails are adapted to help them to swim.
All adult frogs are carnivores by nature. Tadpoles can consume a range of foods. Their diet varies depending on size and species.
Many smaller tadpoles feed on algae or sift through detritus (organic waste).
Others, like the New Mexico spadefoot toad, are voracious predators!
Predatory tadpoles will happily eat anything small enough to be swallowed, including other tadpoles.
You can learn more about tadpole and frog diets in our what do frogs eat article.
A tadpole’s job is essentially to eat as much as it can to provide energy for growth.
There are three main types of feeding in tadpoles depending on the species. Learn more about these tadpole feeding types and frog teeth in general here.
It also needs to evade predators and survive until metamorphosis.
Tadpoles have many predators such as fishes, dragonfly larvae, and even other tadpoles!
We’ll talk more about the secret lives of tadpoles later on in our “Tadpole Life Cycle” section.
Stage 3: Metamorphosis
The transition from the larval phase to adulthood is known as “metamorphosis .”
Many other animals undergo a dramatic morphological overhaul, such as butterflies, crustaceans, and many fishes.
Tadpoles grow rapidly throughout the larval phase, but evidence of transformation starts to appear around five weeks after hatching.
At this point, they begin to sprout hind (back) legs.
The hind legs continue to develop as the young tadpole approaches maturity.
A tadpole’s body also changes to look more frog-like over the course of this time.
Front legs begin to appear around 12 weeks after hatching.
As a tadpole’s legs approach their final proportions, their tail also shrinks as they begin to develop lungs.
Older tadpoles also begin to take larger prey or switch from an omnivorous to a carnivorous diet.
Fully metamorphosed froglets emerge from the water after around 14 weeks.
Froglets breathe air and look almost identical to mature frogs, just smaller!
Some froglets may still have a small tail for a short while after emerging from the water.
This handy Reddit post shows a detailed animation of the transition from tadpole to frog.
Stage 4: Adult Frog
Once frogs have left the water, they instinctively know how to hunt and survive on land.
Most metamorphosed frogs are well adapted for terrestrial life, but they still need access to water.
Some species only require water to breed, while others live close to ponds and lakes to shelter from predators and prevent drying out.
Other frog species, such as the African dwarf frog and the African clawed frog, remain aquatic throughout their entire lives.
All adult frogs need to drink water, which they absorb through their skin.
Reproduction
Frogs can take up to four years to reach sexual maturity.
Around this time, females begin to search for water in which to lay their eggs.
Males develop a specialized vocal sac, which allows them to call and attract mates.
They typically find a suitable water body for a female to lay her eggs in and then call to attract potential mates to the spot.
Female frogs are typically larger at sexual maturity than males. Usually, the size difference is only minor.
Females of some species can be as much as three times larger than males!
Male frogs may also develop bright colors during the breeding season to show off their good health.
When frogs do decide to mate, the male typically grasps the female in an embrace known as “amplexus” and holds on while the female deposits her eggs, fertilizing them externally in the process.
Females of some species will carry their mates around for long periods before laying their eggs.
During this time, frogs are highly vulnerable to predators.
If you’re interested in breeding frogs, check out our list of the best pet frog species.
Unconventional Amphibians
Though all frog life cycles go through the same basic steps, not all amphibians follow the rules exactly!
Pedomorphosis
Some amphibian species – such as the axolotl, mudpuppy, and blind cave salamander – never fully complete their transition.
These species don’t lose their gills. They remain fully aquatic for their entire lifespan.
The retention of larval characteristics through to adulthood is known as “pedomorphosis.”
Interestingly, these species can be forced to undergo “complete” metamorphosis through hormone treatment.
Pedomorphic species or populations benefit from retaining their larval characteristics, as they have a more stable environment with water year-round.
Some species can be flexible, with some pedomorphic populations and some fully metamorphic ones.
Livebearers
Some frogs have evolved to bypass the egg stage altogether and give birth to tadpoles already prepared to swim and forage.
In some species of Nectophrynoides toads, the mother frog retains the eggs within her body cavity until they hatch.
If you’re curious about the difference between frogs and toads, check out our article on the subject.
Somewhat more unusual are the Australian platypus frogs (Rheobatrachus species).
These odd-looking frogs actually swallow their own eggs and hatch them inside of their stomach!
In this case, the female’s stomach stops secreting digestive fluids for the entire period of gestation.
The female frog will retain her young in this way throughout their tadpole phase.
Eventually, the fully-developed frogs can clamber out from her mouth!
Even more strange, perhaps, is the Surinam Toad – or Pipa pipa. These odd-looking creatures embed their eggs within the skin of their backs.
Once fully developed, young Surinam toads erupt through the mother’s skin and swim away!
This Reddit post contains a short clip of a Surinam toad giving birth.
WARNING: This wonder of nature should not be viewed by anyone who suffers from trypophobia (or general squeamishness)!
Tadpole Life Cycle
There’s no true “tadpole life cycle,” per se, but each tadpole undergoes a series of changes before becoming a frog.
- After hatching out of their egg, tadpoles initially remain quite sluggish and inactive. These infant tadpoles still rely on their egg’s nutritious yolk until their mouthparts develop.
- Once the yolk is fully absorbed, tadpoles move into the “swimming” phase. At this stage, they start to use their tail to swim and actively forage for food. Most tadpoles at this stage are herbivores or detritivores.
- As the tadpoles’ mouthparts begin to develop teeth, their diets change. They may start to eat live prey such as insects at this point in life.
- Finally, limbs sprout from the tadpole’s body as it begins its metamorphosis.
Life Cycle of Frog Diagram
No article about the tadpole to frog life cycle would be complete without a helpful diagram!
In our “life cycle of frog diagram,” you can see a visual representation of each stage in the frog life cycle.
Illustration: Max Henderson for Reptile.Guide
It’s certainly interesting to contrast the complex life cycle a tadpole has ahead of it with what a baby axolotl can expect.
Axolotls are neotenic. That is, they retain their juvenile characteristics into adulthood.
Have you found any frogspawn this Spring? Do you know what species it belonged to? Let us know in the comment section!