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Upper Midwest Environmental Sciences Center

Farm ponds as critical habitats for native amphibians
A Field Guide to Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa
Field guide contents

Raising Larvae

If a specific identification cannot be accomplished in the field, raising amphibian eggs or larvae to metamorphosis is one alternative. To appropriately provide for the needs of captive larvae, consult Mattison (1993). We provide a general description of larval care here to familiarize the reader with the procedures involved.

Raising amphibian larvae in an aquarium is not difficult, but avoid overcrowding (raise only one or two animals per ~4 liters [~1 gallon] of water). Water quality is the most important factor. Treat the water as you would for aquarium fish or collect natural pond water or rain water. Tap water contains chlorine, which will kill larvae as well as many fish. Water can be effectively de-chlorinated by letting it stand uncovered for several days. Change the water every few days or as needed. An aquarium or large, shallow container is preferred; the larger the surface area the more oxygen will be available. An airstone is usually not necessary. Do not clean the tank with soap or other cleansers because residues may kill the animals.

Salamander larvae are carnivorous and must be fed an animal diet. Smaller salamanders can be fed “zooplankton” (small invertebrates) netted out of streams or ponds. Larger salamander larvae can be fed small worms (earthworms or tubifex), tadpoles, feeder fish, and even pieces of liver if you wriggle it in front of their mouths. If you feed them liver, remember to not leave any in the container, as it will quickly foul the water.

Frog and toad tadpoles can be raised on a diet of fish flakes or rabbit pellets. Boiled lettuce or spinach, naturally collected algae (be careful not to introduce predaceous invertebrates such as dragonfly larvae or diving beetles), and small amounts of cooked egg yolk can also be fed to tadpoles. Offer these foods daily, but be sure to replace the aquarium water frequently.

The length of time required for metamorphosis varies from several years for American Bullfrogs to a few weeks in the Plains Spadefoot. Some Tiger Salamanders never metamorphose and remain aquatic. Most treefrogs and toads take about two months to develop from eggs to metamorphs. Salamander metamorphosis is less dramatic than frog metamorphosis. Salamanders absorb their gills and any tail fins when they metamorphose. Because amphibians are ectothermic, the temperature of the environment affects their development time. Raise larvae at room temperature or slightly warmer. Light will help maintain the algae that tadpoles feed on; direct sunlight may cause overheating.

If your tadpoles are healthy and developing as expected, you will notice the appearance of hind limbs, then a reshaping of the body, and finally, front limb emergence. At this stage, the tadpole will begin to absorb its tail and many changes will occur both internally and externally as it develops into a juvenile frog. Feeding will cease at some point; the metamorphosing frog is quite vulnerable at this stage. It can no longer swim well, but is not yet able to survive on land. Provide a solid surface area for the metamorphosing animals to climb onto and cover the container to prevent escape. Tilting the container is an easy way to offer both land and water. You may now be able to identify the frog from the developing adult characteristics. If you need to continue to raise your larvae for identification or other purposes, you should feed the froglet or newly-terrestrial salamander tiny insects such as pinhead crickets, wingless fruit flies, or bloodworms, which can be purchased in pet stores.

To prevent the spread of disease to native populations, any frogs or salamanders you raise should not be released back into the environment. Lab-raised amphibians can be anesthetized and euthanized with benzocaine or tricaine methanesulfonate (MS 222, Green 2001). If you anticipate difficulty complying with this guidance, you should not undertake raising larvae in captivity.

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Page Last Modified: December 29, 2010