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From Tadpole to Frog: How long is metamorphosis?

Have you ever seen a frog or toad outside and wanted to know kind it was? Were you unsure about how to figure it out?

Question:

This past spring and summer I saw eggs and then tadpoles at my Frogwatch monitoring site. How long does it for them to undergo metamorphosis and turn into an adult frog? Will they be fully developed before the pond freezes this winter?

© NWF

Answer:

In North America during breeding season, male frogs and toads of most species will gather at permanent and seasonal wetlands, lakes and small ponds, in order to breed with females. Each species has a distinctive song, or call, which males use to attract females to mate. Frog eggs are laid in round masses within the water or as a thin film on the surface of the water and are sometimes secured to twigs or other vegetation. Unlike frog eggs, toad eggs are laid in long strands or strings, often attached to vegetation, and can extend for many feet depending on the species. Once the eggs are laid they begin to undergo the amazing transformation to adults: metamorphosis.

© Ronn Altig

Once the eggs hatch, the young tadpoles continue their development in the water. As tadpoles, the young frogs or toads do not resemble their parents. Instead they have gills and small round bodies with a tail to propel them through the water. While many tadpoles hatch out of their eggs, only a small proportion will ever become adults. Many will become food for other animals such as fish and birds or will die of disease long before metamorphosis is complete.

© William Leonard

Tadpoles are herbivores at this first stage in life, eating microscopic plants and algae. Like fish, tadpoles use gills to breathe and long tails to propel them through the water. When metamorphosis begins to occur, their tails will reduce in size and absorb into their bodies. Gills will disappear as the tadpoles develop lungs. And while the hind limbs have been growing since early on in the tadpole's life, the front legs will pop out close to the time of full metamorphosis. Tadpoles begin to look like their parents more and more from this point on through the remainder of their development. Soon they will appear as miniatures of the adults. It is at this stage that they leave the water and strike out to live on land for the first time.

Most tadpoles complete their development within a few months of hatching, leaving the water and becoming terrestrial before the winter. However, some species such as bullfrogs actually take more than one season to develop and need to overwinter as tadpoles, developing into adults the following year.

© William Leonard

Do you have a question about amphibians? You can ask Amy at Frogwatch USA by sending an email to frogwatch@nwf.org.

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From Tadpole to Frog