FROM THE WOODS
Amphibians
AN EDUCATIONAL SERIES ABOUT FORESTRY FOR YOUTH
Photo: MICHAEL BENARD
W
hat is the most
common animal
found in
Pennsylvania’s
forests? You might think it is
a mammal such as the whitetailed deer or perhaps a songbird such as a sparrow. However, the most common animal
in Pennsylvania’s forests is not
a mammal or a bird at all; it is
one of the Commonwealth’s 39
frogs and salamanders, which
means that it is an amphibian.
Many people think amphibians are animals that live in the
water for part of their lives and
then on land during the other
part, but this is not always true.
Some amphibians never enter
the water. Others lay their eggs
on land under rocks or logs
instead of in ponds. One thing
amphibians all have in common is that they go through
different life stages, with different body forms, as they mature
(“metamorphosis”). This makes
them unique in many ways and
sometimes hard to identify.
One amphibian in Pennsylvania that few have seen
but most have heard is the
northern spring peeper.
Though only a little bigger
than a quarter, it has a
loud, distinctive mating call
described as a high-pitched
whistle. Male peepers sing
in choruses in early spring,
usually near water, and their
vocal sacs look like shiny
bubbles.
Amphibians Are
Vertebrates
Amphibians are animals that
have backbones, like humans
do. But how else are amphibians similar to and different from humans and other
animals? Look at your skin.
Is it wet or dry? Is it hairy
or smooth? Amphibian skin
does not grow hair, feathers,
or scales. Even the “warts” of
a toad are each smooth to the
touch. Amphibian skin is moist
and smooth, which lets it pass
water and oxygen better than
human skin does. Amphibians
never drink with their mouths.
They absorb water through
their skin. Some amphibians
even have a visible patch of
skin on their belly through
which they get their water.
Skin Breathers
Many amphibians are so good
at breathing through their skin
that they do not need lungs.
In fact, 15 of Pennsylvania’s 22
living salamander species have
no lungs at all. Instead of inhaling, these lungless salamanders use the “lung” muscles to
shoot their tongues like slingshots. A fast tongue lets the
salamander catch more insects
than a slow one. The diet of
amphibians varies greatly by
species and life stage. Most are
Eggs in water
Eggs on land
PHOTO: MICHAEL BENARD
PHOTO: ROBERT HILL
Amphibian Eggs
Amphibian eggs can be laid in the water (left) or on land in moist environments (right).
All frogs and some salamanders in Pennsylvania lay their eggs in water. Salamanders
that lay their eggs on land often guard them from predators.
Cover Photo of Eastern red-spotted newt: Brad Wilson, DVM
carnivorous at some stage in
their lives; others have an herbivorous stage.
Protection from
Predators
Although they are small, many
salamanders possess defensive
weapons other than teeth. The
smooth skin of amphibians
is full of glands. One type,
the mucous gland, keeps the
skin moist. In some amphibians mucous glands produce
extra-sticky slime. The slime
of a slimy salamander is sticky
enough to temporarily glue a
hungry snake’s mouth shut. It
might also cause your fingers
to stick together if you handle
the salamander roughly.
Salamanders should never be
handled if you have used your
hands to apply insect repellent
or sunscreen. The same skin
that allows them to breathe
and drink can also allow
chemicals that can harm them
to pass through.
Another trick used by lungless
salamanders is dropping their
tails when they are being attacked. Many lungless salamanders have special blood vessels
in the tail. When the tail drops
off, the blood vessels self-constrict and prevent the salamander from bleeding to death.
The tail then wriggles wildly
and turns the predator’s attention away from the salamander.
Salamanders store fat in their
tails. If the predator does not
find and eat the dropped tail,
the salamander tries to return
and eat its own tail.
A twenty-third species of salamander, the tiger salamander,
Spotted Salamander
northern slimy salamander
Green salamander
used to be found in Pennsylvania’s forests. Tiger salamanders are now considered to be
gone, or extirpated, from the
Commonwealth. It is not legal
to purchase or sell tiger salamanders in Pennsylvania. This
rule will help prevent damage
to native tiger salamanders,
should they be rediscovered in
Pennsylvania.
Tiger salamanders belong to
a group of salamanders called
“mole salamanders.” Four out
of Pennsylvania’s 22 salamander species belong to the mole
salamander family. Just like
the moles that dig in soil, mole
salamanders spend much of
their time under ground. Most
of the mole salamanders come
out of the ground in spring
to lay their eggs in woodland
pools. Mole salamanders use
a second type of skin gland
to defend themselves. Their
heads and tails contain poison
glands that squirt a milky,
bitter chemical mix into the
mouths and eyes of predators.
You should always wash your
hands after handling an amphibian. Their defensive chemicals can be very irritating to
your eyes, nose, and mouth.
Salamanders are not the only
type of amphibian to keep
predators away with skin
gland secretions. All of Pennsylvania’s 14 frogs and toads
are covered with mucous and
poison glands. The warts on
a toad are enlarged poison
glands bundled together to
form a group. Even smoothlooking frogs may have poison glands. The pickerel frog
produces not only a distasteful poison but also an odor.
The smell of the pickerel frog
warns predators before they
bite that its taste will be bad!
Pennsylvania is also the home
of another bad-smelling (“mal-
1
4
2
3
In Pennsylvania, the life cycle of a frog has four stages.
(1&2) Adults mate and lay eggs in water. (3) The eggs
hatch into free-swimming tadpoles. Most tadpoles scrape
algae from the bottom of the pond with a special “beak.”
(4) The tadpole matures into a metamorph, or froglet.
The tail provides energy to the metamorph as it emerges
onto land and develops adult mouthparts. The metamorph
cannot eat until the change is complete!
Illustration: J. B. GRANT
Photos: Brad Wilson, DVM
Photo: MICHAEL BENARD
long-tailed salamander
Many salamanders are so
good at breathing through
their skin that they do
not have lungs. Lungless
salamanders are much
smaller than salamanders
with lungs. Does the spotted
salamander in the top right
photo look bigger than
the others? The spotted
salamander has lungs, while
the rest belong to the family
of lungless salamanders.
american toad
Photo: SANFORD SMITH
Photo: BRAD WILSON, DVM
BULLFROG
What is the difference between a frog and a toad?
A toad is a kind of frog. Frogs and toads both
belong to the same group of animals, the order
Anura. “Anura” means without a tail. There are
dozens of frog families within the group Anura!
We only have four frog families in Pennsylvania.
So, when we think of frogs, we are usually
thinking of frogs in the family Ranidae (the true
frogs, or ranids). North American ranid frogs are
good jumpers with long legs, webbed hind feet,
and smooth skin. When we think of toads, we are
odorous”) and bad-tasting
frog. This frog, the eastern
spadefoot toad, smells like
garlic when handled.
Winter Escape
Eastern spadefoot toads
spend the winter below
ground. They dig deep
enough to escape freezing
temperatures. Other frogs
rely on a good layer of leaf
litter from forest trees to give
them shelter. How does a
frog in leaf litter resist freezing? It doesn’t! Wood frogs
and other leaf-litter users
freeze solid in the winter.
Within 10 minutes of its toetips freezing, the wood frog
sends sugar all over its body.
The sugar slows down the
freezing process. A wood
frog will freeze solid in about
24 hours if temperatures are
right. The sugar also keeps
ice crystals from damaging
the wood frog’s body tissues.
Only about a dozen vertebrate animals in the world
can freeze solid and survive.
Pennsylvania forests are
home to four of them! They
include spring peepers, gray
treefrogs, wood frogs, and
chorus frogs.
So what is the most common animal in Pennsylvania’s forests? It is a lungless
salamander, the red-backed
salamander. This forestdwelling salamander is
often more abundant than
birds or mice. Amphibians
are a key part of our forests. In turn, the shade and
shelter of our forests are
important to amphibians
usually thinking of frogs in the family Bufonidae
(the true toads, or bufonids). True toads have stout
bodies, short legs, and bumpy skin. They are not
the greatest swimmers. Handling toads does not
cause warts. The bumps on their skin are not warts,
but groups of poison glands. In Pennsylvania true
frogs spend more time in or near water than the
true toads. Visit a local pond after sunset during the
spring breeding season (March through May) and
you will see what great swimmers the true frogs are.
because they rely on cool,
moist, and unpolluted environments. When practicing
forest management activities
such as timber harvests and
road building, it is important to protect wetland
areas and bodies of water
that provide valuable amphibian habitat.
Written by Jacqualine Grant, assistant professor of biology,
Southern Utah University, and Sanford S. Smith, extension
specialist in forest resources and youth education, Penn State.
Penn State College of Agricultural Sciences research and extension programs are funded in part by
Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
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