Frogs and toads are among nature's most amazing creations. Hatched in the water from eggs, tiny tadpoles start out life having more in common with fish than land animals. Then limbs start to grow and the tail shrinks, but inside the tadpoles' bodies, an even more significant change is taking place -- lungs are developing. Finally, they stop breathing through gills altogether, rising to the surface of the pond to breathe air, just like we do.
About Frogs, Toads and Their Eggs
Frogs and toads both belong to the same class and order of amphibians. In the same way biologists classify alligators as a type of crocodile, toads are considered to be a type of frog, although members of different families, like cousins with different last names. Frogs belong to the Ranidae family, while toads belong to the Bufonidae family. Both frogs and toads lay their jelly-like eggs in water, where they cling to plants, rocks and aquatic debris. Since these eggs don't have shells, they make easy meals for fish and water insects so the greater the number of eggs, the better the chances that some will hatch.
Frogs Lay Eggs in Clusters
Some types of frogs only lay one egg at a time. More commonly, though, frogs lay their eggs in clusters that swell into transparent orbs as they absorb water and come to resemble bunches of grapes. The numbers of eggs vary from one type of frog to the next but the American bullfrog's clusters typically consist of about 12,000 eggs that hatch in less than a week. Most other kinds of tadpoles mature into frogs in a few weeks but bullfrog tadpoles, which are much larger than other tadpoles, take up to three years to become froglets, the name for baby frogs.
Toads Lay Eggs in Strings
Toads lay eggs that look like black beads connected in long stringy chains encased in a clear jelly. The numbers of eggs laid by North American toads vary. The eastern American toad lays 2,000 to 20,000 eggs in two strings, with partitions between each one. The Fowler's toad also lays eggs in a double string, with a total of 7,000 to 10,000 eggs, but without partitions separating them. The all-time egg-laying champion is the cane toad, laying up to 35,000 eggs at a time around water plants near the pond floor.
Frog and Toad Populations in Decline
Frogs and toads play very important roles in maintaining a healthy balance in the ecosystems where they live, but populations are in decline, not only in North America but also all over the world. According to author David P. Badger in his book "Frogs," up to 95 percent of the eggs laid by frogs and toads never hatch. In addition to being eaten by predators, eggs can be destroyed by heavy rain and sudden freezes. Pollution from herbicides, pesticides, acid rain and the thinning ozone later, threaten the survival of fragile eggs and tadpoles, as well, Badger states.
- Department of Wildlife Ecology and Conservation: UF Wildlife -- Johnson Lab: Frog Egg-Laying Habits
- Wonderopolis: Are Frogs and Toads the Same?
- Franklin Institute: Something Froggy: Frogs and Toads
- Virginia Cooperative Extension: Sustaining America's Aquatic Biodiversity - Frog Biodiversity and Conservation
- Prince William Conservation Alliance: Northern Virginia Wildlife: Frogs & Toads
- Frogs: David P. Badger: Voyageur Press: Excerpt
- Online Field Guide: Cane Toad
- Frogs; David P. Badger; 1995
- Online Field Guide: Cane Toad
- Digital Vision./Photodisc/Getty Images