How to Raise a Tadpole into a Frog
Watching the process of amphibian metamorphosis is fascinating. Here are some tips to assure that tadpoles survive, grow, and develop.
In the spring and summer months, the sounds of amphibian calls fill the air, and it is not unusual to find frog or toad eggs sitting in ponds and puddles. Many summers of my youth were spent collecting eggs or tadpoles and attempting to keep them alive long enough to watch them go through metamorphosis and turn into frogs or toads. Rearing these critters is easy enough, if you know a few important tips.
Tadpoles will not survive for long if they are placed in tap water containing chlorine. I suggest using water directly from the pond, if possible. If that is not feasible or convenient, there are water treatments that can be purchased that are the same as those in fish tanks. The easiest thing to do, however, is to set a bowlful of tap water in the sunlight for a day or so, which will remove the chlorine and make it habitable for the tadpoles. The water should be changed at least twice per week, to prevent the buildup of waste products that can eventually kill the animals.
Tadpoles need a bit of space to grow and develop properly. This means there should be no more than five or so tadpoles per gallon of water. If they are more crowded, they will survive, but they may not develop into little frogs.
Tadpoles should be fed after every water change. A simple flaked fish food has enough nutrients and is cheap and easy to find.
The amount of time it takes for a tadpole to develop into a frog or toad depends on the species. Some species, such as spadefoot toads in the desert southwestern United States can go through metamorphosis in just over a week, while bullfrogs in the northern US might take upwards of three years. So, unless you want to spend a long time watching your tadpole grow it might be a good idea to find out which species your dealing with. A good rule of thumb is if you find small tadpoles in the spring, they are likely freshly hatched and will transform sometime before the end of summer. Large tadpoles in the spring, or small tadpoles in the summertime might mean you have a species that will take more than a single year.
As the tadpole begins to go through metamorphosis, you will notice small legs forming where the tail and the body meet. These back legs will become longer and more defined as the tadpole goes through metamorphosis. The front limbs form at the same time as the rear limbs, but they form inside the body and so are invisible until metamorphosis is nearly complete.
Once the tadpole's rear limbs are very developed, and look like an adult frog's limbs, it is important to put something that floats into the vessel containing the tadpole. Once the tadpole reaches metamorphosis and becomes a frog, they no longer have gills and can drown. It might also be important at this stage to put a screen on the top of the vessel to assure the newly transformed frog does not escape. Once the front legs are apparent (this can happen quickly!), metamorphosis is complete, and over the next few days the tail will slowly absorb into the body until it eventually disappears.
Once you have enjoyed watching your frog transform, you can choose to release the animal, or keep it as a pet. It is very difficult to keep a small froglet or toadlet alive, because they require living food, which is hard to come by in a size small enough so that it will fit in its mouth. Thus, it is usually best if you release the animal. If you do decide to release your frog or toad, make sure to release it in or near the pond or place in which you found the tadpoles. Many frogs are adapted to specific locations, and not all species are found in all ponds.
Hopefully using these tips will be useful for anyone wanting to observe the miraculous process of metamorphosis!