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Green treefrog tadpoles
Coined “Year of the Frog” by zoos and aquariums across the globe, 2008 has been dedicated to celebrating and saving the world’s 6,000 amphibian species, one-third of which currently face extinction. At such an important time, it is with great excitement that the Chicago Zoological Society (CZS), which manages Brookfield Zoo, announces the late-June and early-July hatchings of more than 300 green treefrog tadpoles. The youngsters, which were about the size of a grain of rice at birth, can be seen inside the Feathers and Scales: Birds and Reptiles and Hamill Family Play Zoo exhibits, and everyone is invited to watch as the tadpoles transform into full-fledged, adult frogs by early to late-September. Once the tadpoles mature to frogs, they will be sent to other zoological facilities.

When it comes to amphibians, the phrase “double-life” takes on a whole new meaning. Although green tree frogs spend time both on land and in water, there are actually two distinct stages of frog life—a larval (tadpole) stage and an adult stage. The transformation from tadpole to frog is called metamorphosis, and this complex process can be amazing to witness.

Green treefrog tadpoles When ready, frogs lay their eggs in water in large, floating clumps called spawn. Hundreds, sometimes thousands, of eggs are laid at once in order to ensure survival of the species. Eventually, tadpoles already well adapted for an aquatic lifestyle hatch from the eggs, complete with tail and gills. This is the current stage for the 300-plus tadpoles at Brookfield Zoo. However, in the next few weeks, the tadpoles will undergo many exciting changes. They will begin growing hind legs, then their front legs. The tadpoles will also start to lose their gills and develop lungs to help prepare them for life on land. They will then lose their tails and become fully formed young frogs. After about a year, they will reach an adult size of 2 to 2.5 inches in length and live up to eight or nine years.

It has been five years since Brookfield Zoo welcomed green treefrog tadpoles, and the hatchings of more than 300 hundred are a wonderful story in terms of conservation. With amphibian species continually being threatened by habitat loss, climate change, pollution, and other serious issues, having so many tadpoles is a great chance to educate the public about amphibians and their extinction crisis.

Says Mark Herbert, senior zookeeper for CZS, “Not even our common species should be considered common anymore—all could be endangered soon.”

Guests desiring to view amphibian metamorphosis in action are encouraged to space their visits to two or three weeks apart. This will increase the likelihood of seeing noticeable differences in development from limbless tadpoles to tiny frogs. Roving Naturalists and docents will be available at each exhibit to discuss metamorphosis or answer any questions guests may have. You can also learn more about the Year of the Frog campaign, and help amphibians across the globe.

Green tree frogs are commonly found from Delaware south along the coastal plain into Florida and the Keys, west to eastern Texas, and north through central Arkansas and west Tennessee to southern Illinois. They like trees and shrubs near wetlands, lakes, streams, and ponds. They are recognized by their green color, by the defined white or yellow stripes along each side, and sometimes by the small yellow or orange spots on their back. These slender, long-limbed amphibians have webbed toes and large adhesive, suckerlike discs on the tips of their toes for climbing. The adults have a pretty impressive chorus during the spring and summer months that can at times seem almost deafening.