toads and frogs in the field guide.
EASTERN AMERICAN TOAD
Anaxyrus americanus americanus (formerly Bufo americanus)
NORTHERN LEOPARD FROG
Lithobates catesbeianus (formerly Rana catesbeiana)
Anaxyrus woodhousii woodhousii
COLORFUL, HARMLESS, VOCAL AND VALUABLE
Missouri forests, prairies, rivers, swamps and marshes are home
to a multitude of toads and frogs, but few people know how many
varieties we have, how to tell them apart, or much about their natural
GOOD INDICATORS OF ENVIRONMENTAL HEALTH
Their role in nature can be illustrated by the huge number of insects
they eat and by the number of animals that eat them or their tadpoles.
Since their bodies readily take in contaminants, they are good indicators
of environment health. Amphibian skin secretions also are used in
medical research to control and cure human diseases. And a discussion
of the value of frogs should include the fact that thousands of
bullfrogs are harvested in our state each year for human consumption
one of Missouris truly gourmet outdoor foods.
All Missouri toads and frogs must return to a body of water to reproduce.
Most species breed during the late winter, spring or early summer,
but southern leopard frogs, Rana sphenocephala, are also known to
breed during rainy periods in the autumn. The majority of these
amphibians select fishless bodies of water for breeding. Flooded
fields, ditches, woodland and prairie ponds, and temporary pools
are favorite breeding places. A few adventurous males locate an
appropriate breeding pond when the temperature and humidity are
suitable and begin to call. Each species of toad or frog has a distinct
breeding call that entices females to join them and select a mate.
Soon, other males congregate and add their voices to the chorus.
Females, heavy with eggs, enter the pond and are grasped by a male
in an embrace called amplexus and begin the process
of egg-laying. During egg-laying, the males vent opening is
positioned just above the females vent, and as her eggs are
released, the male fertilizes them with his milt. He will retain
his firm grip on her until all the eggs have been laid.
From tadpole to adult
Most eggs hatch within 10 to 14 days of being laid, but they may
hatch much sooner if the water temperature is above 70 degrees F.
The tiny, newly hatched tadpoles rest for a few days by clinging
to aquatic plants, receiving nourishment from the last of the yolk
sac stored in their bellies. Most Missouri tadpoles eat aquatic
plants especially algae as they develop in the wetland.
Tadpoles have gills, somewhat like fishes' gills, which are covered
and protected by a flap of skin. As development progresses, the
hind legs form and enlarge. The tail begins to shrink at this stage.
As the front legs appear, the tail continues to become smaller.
Soon the gills are not used and the late-stage tadpole begins to
breathe air at the surface, using brand-new lungs. The final stage
of development from a tadpole to a young frog, known as a froglet,
is the combination of the disappearance of the tail and the change
from a life underwater to a life on land or along the edge of a
pond or swamp. Soon after transforming from tadpoles to froglets
or toadlets, these young amphibians begin eating insects, small
spiders and worms. They grow quickly.
Toads and frogs defend themselves in several ways. Most of their
predators are fish, turtles, snakes, birds and carnivorous mammals
shrews, mink, skunks, and raccoons. Missouris larger
species of frogs also will eat other frogs.
Toads cannot jump as fast as frogs. To escape a predator, toads
defend themselves by producing toxic or unpleasant-tasting skin
secretions that are released when the animal is seized. Due to their
toxic skin, toads are not a popular food among most predators. Even
their eggs and tadpoles are said to be toxic.
Frogs also have skin glands which cause them to have a bad taste.
But the secretions are not generally as strong as those of toads,
so frogs are eaten by a much wider variety of predators. People
normally are not affected by the skin secretions of toads and frogs,
though human eyes are sensitive to these substances. The pain and
burning that result when even a slight amount of skin secretion
gets in one of your eyes is something you will never forget.
It is important to wash your hands after handling a toad or frog.
The age-old myth that toads can cause warts on people is false.
Toads and frogs are amphibians a class of vertebrate animals
that also includes salamanders and the tropical caecilians, which
are long, slender, wormlike, and legless.
Missouri has 26 species and subspecies (or geographic races) of
toads and frogs.
Toads and frogs differ from salamanders by having relatively short
bodies and lacking tails at adulthood.
Being an amphibian means that they live two lives: an aquatic larval
or tadpole stage and a semi-aquatic or terrestrial adult stage.
Of the 6,145 species of amphibians currently recognized in the
world, there are approximately 4,145 species of toads and frogs.
The largest species is the goliath frog, Conraua goliath, of the
west coast of Africa, which may have a head-body length of nearly
14 inches and may weigh as much as 7 pounds.
One of the worlds smallest frogs is Eleutherodactylus iberia,
which has no common name and lives in the tropical forests of Cuba.
It is less than a half-inch long as an adult. This frog is so tiny
that females of the species are able to produce only one egg during
the breeding season.
DIFFERENCES BETWEEN TOADS AND FROGS
Even though they are more similar than different, there are some
basic physical distinctions.
- Dry, warty skin
- No teeth
- Shorter hind legs than most frogs
- Hop or crawl
- Lay eggs in long, parallel strings
- Smooth, wet skin
- Tiny teeth on both upper and lower jaws
- Jump or leap
- Lay eggs singly, in small clumps, in large masses, or as a film
of eggs on the water surface
TOAD AND FROG CALLS
With practice, you can learn to identify a variety of toads and
frogs by the sounds they make. A male toad or frog produces his
call by a rapid back-and-forth movement of air over his vocal cords.
When calling, a toad or frog will close its mouth and nasal openings
and force air from its lungs over the vocal cords into the mouth
cavity, then back over the vocal cord and into the lungs. Producing
a sound in this closed system enables some toads and frogs enlarged
throat or expandable vocal sac to resonate their calls.
Toads and Frogs Brochure (pdf, 3 MB)