WEATHER BRINGS MORE FROG QUESTIONS
December 13, 2009
because of the exceptionally rainy weather or some other reason, I have
received more questions about frogs and toads than usual. Michael Dorcas,
an amphibian biologist at Davidson College, Charlotte, N.C., has also
noticed an increase in questions. The following are our answers to some
of those questions.
are the most species of frogs and toads found in the United States?
the greatest biodiversity of U.S. frogs and toads is in the southeastern
states from the Carolinas to Florida, Georgia, and Alabama. Each of those
states has at least 30 species of native frogs, which is more than any
of the western states.
Q. Why do
so many frogs have long legs?
have comparatively longer legs, particularly the hind legs, than any other
group of vertebrate animals. Some species of frogs have much longer legs
than others, but the hind limbs are longer than the front limbs in all
species of frogs. Toads generally have shorter legs in proportion to their
body than the true frogs or the treefrogs, but even toads have hind legs
that are relatively longer than their front legs or than the hind legs
of most other animal species. The most obvious reason for having strong,
elongated hind legs is that they allow the animal to jump long distances
relative to its body length. Jumping, which aids in rapid transportation,
is especially effective for escaping from predators, thus offering a significant
advantage to an otherwise vulnerable prey species. The single adaptation
of jumping, or saltatory (proceeding by leaps) locomotion, is considered
by many amphibian biologists to be responsible for the worldwide success,
that is, high biodiversity, of this group of amphibians. The powerful
hind legs of some frogs are used not only for jumping but also for swimming.
A large bullfrog can jump several times its body length from a riverbank
into the water, and its strong legs and large webbed feet can then be
used to propel the frog rapidly underwater. The long legs of treefrogs
are used for reaching out to grasp the next leaf or tree branch.
Q. How far
can frogs jump?
A. Many frogs
can jump at least 30 times the length of their body, and some of the smaller
species of treefrogs can probably jump more than 50 times their own length.
This would be equivalent to a human jumping the length of a football field
without a running start (as if a running start would really matter that
much). Although the exact record is disputed, a couple of larger species
within the family Ranidae, which includes the bullfrogs and leopard frogs,
have been reported to jump more than 30 feet from a sitting position.
Some of the frogs in the genus Rhacophorus, the so-called flying
or gliding frogs in Asia, can go the longest distances, depending on the
height they jump from, because they actually glide through the air. Because
jumping long distances is important to the survival of many species of
frogs for predator avoidance, the skeleton of some species is modified
to absorb shock when they land, although the force of landing for small
frogs is of little consequence. Some frogs, such as the narrow-mouth toads
of the Southeast or the Mexican burrowing frogs, can only hop a few inches
Q. Are frogs
A. Most frogs
have moist skin, and frogs closely associated with aquatic habitats typically
have slimier skin than do those that are found on land in drier areas.
Some frogs produce mucus that makes them so slimy that they are difficult
to hold on to, which allows them to escape from some predators. All tadpoles
are slippery. Frogs have lungs, but many species also breathe by transporting
oxygen from the air across the skin. For this form of respiration to occur,
the skin must remain moist. In general, toads have drier skin than do
other frogs, but there are a number of exceptions to this rule. Many frogs
and toads produce toxins in the skin that make them unpalatable to some
predators. This toxin is mixed in as part of the "slime" on
the back and legs of poisonous frogs.
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