Fermilab Frog FAQs

So what makes a frog a frog? Frogs and toads are amphibians, which means they live their lives both in water and on land. Typically, frogs breed and spend thiertheir [sic] juvenile (or "larval") stage in the water, then spend some or virtually all of their adult lives on the land. Frogs and toads are distinguished from salamanders (which are also amphibians) by the fact that adults do not have a tail.

Do all frogs live in the water? No. The amount of time that adults spend in the water varies enormously. Bullfrogs and green frogs, although they have lungs and breathe air, spend almost all their adult lives in the water. On the other end of the spectrum, toads and treefrogs spend the majority of their adulthood outside of water. All frogs and toads, however, must eventually come back to the water to mate and lay eggs.

Why do the eggs have to be in water? Amphibian eggs do not have a hard protective shell like bird or reptile eggs. Frogs and toads lay eggs in jelly-like masses, and unless the eggs are covered with water, they will dry up and die. Most amphibian eggs become much bigger after they are laid because the eggs absorb water and swell to several times their original volume!

What are tadpoles? Tadpoles are the immature (larval) forms of frogs that hatch right from the egg. All tadpoles are completely adapted to live underwater. Like fish, they breathbreathe [sic] through gills rather than lungs. Tadpoles eventually transform themselves through a process called metamorphosis into adult frogs. Hormone changes within their bodies cause their legs to develop and their tails to be re-absorbed into their bodies. Wow!

What do frogs eat? Adult frogs and toads are always predatory, preying on insects mostly but also smaller frogs and fish. Tadpoles are mostly vegetarian, grazing on algae that grow in leaf or rock surfaces under the water. Sometimes, very large tadpoles, such as bullfrog tadpoles, become meat-eaters and sometimes even eat other frogs!

Does anything eat frogs? Tadpoles can be a significant food item for fish, mammals, and even other adult frogs. Adult frogs are preyed upon by snakes, raccoons, herons, and other terrestrial (land-based) predators.

So whatÕswhat's [sic] the difference between a frog and a toad? There are no hard and fast rules, but in general: Toads have dry, warty skin and relatively short legs for hopping. Frogs have smooth, damp skin and long legs for swimming or leaping.

Can toads really give you warts? Toads do not give people warts. Amphibians have many glands in their skin, and several species produce highly toxic secretions for protection. Toads do secrete a substance from the skin that can be very irritating if it comes into contact with mucous membranes like the eyes, nose, mouth, etc.

How do frogs make their calls, or "ribbets"? In some species, such as Spring Peepers, the lower part of the mouth can become a large resonating vocal sac. When the frog closes its mouth and nostrils, and then forces air from the lungs over the vocal chords, the sac inflates and vibrates like a drum, producing long, loud trills. Other species just produce calls with the vocal chords.

Why do frogs call? Frogs and toads make a variety of sounds, depending on the situation. The most common are "advertisement" calls, and "alarm" calls. Frogs and toads advertise their presence either to ward off challengers to their territories, or to attract mates. Alarm calls serve to startle predators.

How can I find frogs? Frogs can be very difficult to find. They are usually highly camouflaged, blending into their environment. The easiest time to locate frogs and toads is during the mating season. During this time they are in the water, and calling, so it's often easier to hear frogs than to see them. Breeding season can vary depending on the frog species and on local weather conditions.

How many kinds of frogs can be found at Fermilab? Northern Illinois has a pretty small amphibian population. Only about a dozen frog species are commonly found around here, and only six to eight species can be found at Fermilab.

Why are frogs so sensitive to pollution? Beginning in the early 1980s, biologists began to realize that amphibians such as frogs are extremely sensitive to pollution and other environmental stresses. Declines in amphibian numbers and increases in deformed bodies have led scientists to investigate the role of habitat loss, increased ultraviolet radiation (due to ozone depletion), and chemical pollution in these important changes. No one is sure why amphibians are so sensitive to pollution, but it may be linked to the fact that their skin is relatively thin and permeable to water, so frogs are exposed more directly to pollutants and environmental radiation. In addition, their eggs are laid in ponds and other water bodies, so they can absorb whatever chemical pollution may be present throughout their early developmental period.

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Designed by Rory Parilac, Content by Rod Walton To ask questions about frogs, email Rod Walton ([mailto:rwalton@fnal.gov rwalton@fnal.gov]) Web Maintainer: [mailto:ed-webmaster@fnal.gov ed-webmaster@fnal.gov] Last Update: August 10, 2001