1. Individual treefrogs can change color between green and
brown tones in a few minutes. This color change is related to
the temperature and amount of moisture in the air, not to the
background color as is the case for most reptiles.
(Photo by Jon McGinnis.)
Frogs, along with salamanders and newts, are members
of the animal group called amphibians. Amphibians (from the Greek
words amphi, meaning "both," and bios or "life") are fittingly named.
Frogs start their lives as totally aquatic animals with gills and
a pronounced tail fin; this is familiar to many people as the tadpole
stage. Over time, legs develop, the tail and gills are absorbed,
and the frog becomes a terrestrial, air-breathing animal (Fig. 2).
The Pacific treefrog (Pseudacris regilla,
Fig. 1) is the smallest but most commonly
seen and heard frog in Washington, and for that reason much of this
handout is devoted to it. For information on the other native species
of frogs, see Table 1.
The Pacific treefrog is an adaptable species found
from rainforests near sea level, to mountains at 11,000 feet, and
on into dry interior areas of Washington where water is available.
Adults measure 2 inches in length and vary in color from a bronze
brown to a light lime green, and from solid in color to intricate
patterns. A sharply defined black mask extends from the tip of its
snout to its shoulder.
The "song" or call of the male treefrog, designed
to attract females, is a loud, two-part kreck-ek, or a ribbit,
often repeated many times. This calling stimulates other males to
join in, and large concentrations of these frogs can be heard far
away, especially on nights when air temperatures remain above 45
degrees. Male treefrogs call mainly in the evening and at night,
although they often call sporadically during the day at the height
of the breeding season. A dry-land call made by male treefrogs away
from their breeding ponds is a single-note Krr-r-r-ek.
When Hollywood moviemakers wanted frog calls to
convey the feeling of nighttime outdoors, they recorded treefrogs.
Consequently the "ribbit-ribbit" calls of this species have
become the stereotypical frog call, even in areas where treefrogs
about Washington Treefrogs
Needs of Adults
on location, treefrogs move into breeding sites from February
(coastal areas) to July. Breeding sites include ponds, swamps,
marshes, and roadside ditches—even puddles that dry up
during the warm months.
of the breeding season, adult treefrogs inhabit a variety of
habitats, including woodlands, meadows, pastures, and gardens—at
times several hundred yards from water. Note: Ponds,
swamps, marshes, and similar spots are used only a few weeks
or months of the year; treefrogs spend the rest of the year
in surrounding areas.
dry periods and in arid areas, adult treefrogs are active only
at night, spending the day in water or shaded vegetation, a
rock or log crevice, rodent burrow, or other protected place.
secrete a waxy coating from their skin glands that allows them
to remain moist and travel far from water.
- Toe pads
on their front and hind toes enable treefrogs to climb in search
of beetles, flies, spiders, ants, and leafhoppers. Adults have
been seen and heard up in trees and outside windows two stories
treefrogs catch prey with their long, elastic-like, sticky ended
tadpoles eat algae, decaying vegetation, and scavenge on dead
earthworms, fish, or whatever else is available.
2. The various life stages of a treefrog.
(Adapted from, Corkran, Amphibians of Oregon, Washington,
and British Columbia: A Field Identification Guide.)
and Life Cycle
- Male treefrogs
are the first to move into their aquatic breeding areas and
soon begin chorusing to attract females. Males chorus while
floating at the surface or sitting partially submerged in shallow
lay 400 to 750 eggs, which are externally fertilized by the
egg masses contain 10 to 75 eggs, measure 1 to 2 inches across,
and are surrounded by a special jelly that swells up on contact
- Egg masses
are attached to sticks or grasslike vegetation below the surface,
or may be on the bottom in shallow areas. Egg masses often become
camouflaged with algae and sediment.
- Eggs hatch
more quickly in warmer water, with the time averaging two to
- Tiny hatchlings
soon turn into tadpoles with short, round bodies and eyes that
bulge out at the sides of their heads (Fig. 2).
- In five
to six weeks, tadpoles turn into 1/2-inch long, air-breathing
juvenile frogs that climb onto land but eventually return, like
their parents, to breed in water.
populations are notorious for dramatic year-to-year fluctuations.
They may not breed at all if the rainy period of the year is
too short, as happens in some droughty years.
eggs are eaten by caddisfly larvae and fish. Fungus and frost
also kills some eggs.
tadpoles are eaten by dragonfly larvae, diving beetles, fish,
long-toed salamander larvae, bullfrogs, garter snakes, and birds
(herons, ducks, and jays).
- On land
and at the water's edge, raccoons, foxes, coyotes, river
otters, skunks, snakes, hawks, and owls eat adult treefrogs.
Cats, children, lawn mowers, and vehicles all take their toll
on adult treefrogs.
- The loss
of wetlands and natural ponds eliminates breeding areas; chemicals
from pesticides and runoff poison treefrogs and their food.
- Most treefrogs
die at the egg or tadpole stage, hence having a life expectancy
of only a few weeks. Treefrogs that reach adulthood live an
average of two years in the wild.
1. Native Frogs of Washington
3. The Red-legged frog can be as much as 4 inches
long and gets its name from the deep wine-red (burgundy) undersides
of its legs, thighs, and portions of the belly.
(Washington Dept. of Fish and Wildlife.)
4. The Oregon spotted frog occurs in a handful of
localities in the Puget Sound lowlands.
(Photo by William Leonard.)
5. The native Northern leopard frog populations have
declined dramatically and this frog has been wiped out in much
of the Pacific Northwest. (Washington Department
of Fish and Wildlife.)
In the cooler,
more moist areas of Washington, the frogs you are likely to hear
or see are the treefrog and red-legged frog; in arid areas the
dominant species are the treefrog and the spotted frog. The following
are descriptions of these and other less common species:
frog (Rana aurora, Fig. 3) is fairly common west of
crest of the Cascade Range. It inhabits moist forests near cool
ponds, lakes, and slow streams, especially where aquatic vegetation
provides cover. During the nonbreeding season this frog may be
found several hundred yards or more away from permanent water.
It can be as much as 4 inches long and gets its name from the
deep wine-red (burgundy) undersides of its legs, thighs, and portions
of the belly.
is a series of five to seven quiet, low-pitched notes—uh-uh-uh-uh-uh.
Males often call from under water and the call is barely audible
when made above water.
spotted frog (Rana luteiventris) occurs east of the
Cascade mountains in marshy edges of permanent ponds, lakes, and
streams. Adults are 3 inches long and light to dark brown, gray,
or olive green, with dark spots on their back, sides, and legs.
The undersides of their legs are bright red, salmon, or orange.
Their upturned bright-yellow eyes are characteristic of this frog.
It is uncommon to hear this frog call, but it may allow you to
observe it closely. Its call is a rapid series of 5 to 30 faint,
low-pitched, hollow notes that sound like a distant woodpecker
tapping on hard, resonant wood.
The species formerly known as the "spotted frog" has
recently been separated into this species and its near relative,
the Oregon spotted frog (Rana pretiosa, Fig. 4).
The Oregon spotted frog is similar in appearance and occurs in
a handful of localities in the Puget Sound lowlands.
frog (Rana cascadae) occupies mountain meadows and
moist forests above 1,500 feet. This frog breeds in marshy bogs
or ponds, often along the margins of slow-moving mountain-meltwater
streams. It is 2-1/2 inches long and olive to brown, usually with
black spots on its back and legs. The undersides of the adults'
legs are yellow. Its call is a series of low-pitched clucking
leopard frog (Rana pipiens, Fig. 5) occurs only in
a few areas in eastern Washington. Their populations have declined
dramatically and they have been wiped out in much of the Pacific
Northwest. This frog reaches 4 inches in length and is easily
recognized by the large, dark spots with pale borders on its back,
sides, and legs. Its call lasts several seconds and consists of
a series of low-pitched snorts or grunts that have been compared
to the puttering of a small motorboat.
to be more active at lower temperatures than snakes and lizards.
As a result, they can be seen in the fall and early spring when
most reptiles are in a hibernation-like state. On warm, rainy
nights during spring and fall, search trails, roads, and other
openings for adult frogs (and toads) on the way to or from breeding
Examine ponds, swamps, marshes, and other bodies of fresh water
from February through August for breeding adults, eggs, tadpoles,
or juveniles. Slowly and quietly approach the area, using binoculars
to detect animals visible along the waterline or the characteristic
dual eye-bumps of frogs on the water surface.
Adult and juvenile frogs are usually found at the surface, at
the water's edge, or in moist vegetation along the shore.
Recently metamorphosed juveniles often are found under objects
around the edges of the water. Occasionally, after rains, they
can be found moving into upland areas near breeding sites in large
numbers. When examining areas under rocks, wood, and other material,
always carefully replace the covering in its original position.
Breeding sites for frogs are often located in the warmest water
locations, including water within or adjacent to thin-stemmed
emergent plants such as rushes, sedges, and aquatic grasses. Tadpoles
are found near large pieces of wood or rocks that store heat.
Likewise, they tend to cluster in the warmest water they can find—often
in shallow areas with lots of sun exposure.
Most frogs start to call about half an hour after sunset. Calling
also occurs during dark and rainy days. When listening to identify
a frog species, remember that the calls are generally slower in
colder temperatures, and faster when it is warm. (See individual
species descriptions for specific call information.)
Handling frogs can be hazardous to their health and needs to be
done carefully—or not at all. Their permeable skin could
absorb harmful chemicals from your hands, such as lotion or bug
repellent. Amphibians can also die from moisture loss, known as
desiccation. Handling them increases this risk. (See Collecting
and Releasing Amphibians.)
and Maintaining Amphibians on Your Property
their total habitat requirements extend from water onto the land,
it is difficult to maintain wild frogs and other amphibians in
most yards. If your yard is surrounded by concrete and highly
maintained landscapes, chances are slim that these interesting
animals will visit.
The chances of hosting frogs and other amphibians increase if
your property adjoins an undeveloped area, such as a greenbelt
or other wild area, or if it is next to a wetland, stormwater
retention pond, or other freshwater area. Your chances further
increase if you establish and maintain a natural landscape. Treefrogs
are very good at colonizing new areas.
for Frog Watchers
are some hints for frog watchers heading into the field:
If you frog-watch alone, let someone know where you are
going and when you plan to be back.
Don't wade out into ponds or marshes—you will
scare the frogs, and there is the risk that you may slip
and fall into the water.
Keep a close eye on children.
Have a change of clothes just in case you get wet.
Watch for stinging insects. If you have an allergy to
stings, be absolutely sure you have your sting kit with
Use polarized sunglasses and binoculars for better viewing.
If you are frog-watching on private land, ask permission
from the landowner.
Make sure dogs are leashed—better still, leave them
and maintain amphibians on your property:
Protect existing natural areas to the greatest extent possible.
Protect woodlands, wetlands, meadows, stream corridors, shorelines,
and other wildlife habitat on your property; encourage your friends
and neighbors to do the same. Support public acquisition of greenbelts,
remnant forests, and other wild areas in your community. Write
to legislators and attend public meetings when regulations are
Protect buffer areas next to streams, lakes, or ponds.
The vegetated buffers surrounding these areas protect the ecological
functions and value of the breeding habitat, and provide needed
upland habitat for amphibians.
Wherever possible, protect migration paths between uplands
and breeding sites. If amphibian migrations to breeding sites
cross neighborhood roads, try placing signs to inform local drivers
of this crossing. If a new road is to be constructed in migration
areas, work for installation of amphibian crossing structures,
such as small tunnels under the roadway. Amphibian movements can
also be guided by means of drift fences and large logs. If you
have an area on your property that is used by migrating amphibians,
leave the area as natural as possible.
Leave a portion of your grass unmowed, especially in areas
that adjoin a wet area, forest edge, or any other distinct habitat,
as well as any area that is being used by migrating amphibians.
If you must mow in these areas, mow at slower speeds and be ready
to step on the clutch or brake. Set the mower blades as high as
possible, or use a weed-whacker and leave grass 6 inches high.
Regularly mow any areas you want to keep as lawn to prevent
longer grass developing where frogs may hide. Mowing in hot,
dry weather will minimize the chances of finding amphibians, and
making some disturbances before mowing may encourage frogs to
hop out of the way. Don't mow or weed-whack when many amphibians
are seen breeding migrations or juvenile dispersal periods.
Preserve leaf litter under trees and shrubs. Such material
provides cover and moisture; it also attracts organisms that amphibians
6. Retain stumps, logs, rootwads, rock piles, and other
debris that provides a cool, moist habitat for amphibians.
(From Link, Landscaping for Wildlife in the
stumps, logs, rootwads, rock piles, and other debris that provides
a cool, moist habitat for amphibians. Such habitat features
provide much needed cover. All these can be strategically located
as "stepping stones" across exposed areas, or to bridge
gaps between breeding ponds and woods. To be effective in exposed
areas, keep the structures within 15 feet of each other.
With permission from landowners, you could salvage these materials
from cleared or logged areas and install them in your landscape,
preferably away from busy roads (Fig. 6).
building a pond. Treefrogs will breed in almost any type or
size of pond. If your pond is aimed at amphibians in general,
however, it is critical not to stock fish, given the problems
with predation and the increased nutrient load that may result.
For fish lovers, one option is to build a separate pond specifically
Fence large ponds to prevent access by livestock, to protect
the water, and to allow a more diverse plant community to grow,
providing cover for amphibians and their food source.
Avoid using pesticides and herbicides. Amphibians have
highly permeable skin that can absorb toxic chemicals from your
lawn, and they can be poisoned directly or indirectly through
their food, such as slugs and snails. Moss-killers and roof treatment
chemicals can also be toxic, and often such runoff is directly
channeled into wetlands via pipes or sewer outflows.
and Releasing Frogs
If frogs are not present in your yard, there is probably a good
reason. Generally, the conditions surrounding your property are
not right for them. Attempting to move a frog into your yard when
conditions are not appropriate for it will probably result in
killing the animal.
Another reason for not relocating these animals is their well-developed
homing instinct. Many will immediately leave an unfamiliar area
and, drawn by instinct, try to return to their place of origin.
This usually results in their being killed on roads or by predators
they are exposed to on their journey.
If you enhance your yard for frogs, and if they occur naturally
in your general vicinity, sooner or later you will probably enjoy
seeing them on your property. Meanwhile, work with the wildlife
species that do visit your property and help preserve nearby wild
Many frog species are popular as pets. Unfortunately, owners often
tire of them and release them (illegally) to fend for themselves
(see Legal Status). Many of the pet-store
species cannot survive our climate and will die if released. On
the other hand, some species, such as the bullfrog often do survive.
They may introduce new diseases or compete with native frogs and
7. The male treefrog amplifies his voice with a resonating
throat sac he blows up to three times the size of his head.
(Washington Department of Fish and Wildlife.)
one or more treefrogs may be annoying to some people, particularly
light sleepers (Fig. 7).
If for some reason the presence of frogs cannot be tolerated,
or to exclude them from an area where they might be injured or
killed, install a barrier. Aluminum hardware cloth, or another
type of rust-resistant material, can be used to surround a pump
or other mechanical device within the pond to eliminate mortality.
This will need to be maintained regularly. Note: a fence will
not keep treefrogs out.
To prevent frogs from breeding in a small pond, keep it empty,
or keep a waterfall or other source of turbulence in place to
discourage frogs from using it during the breeding season. Egg
masses can also be removed, as can adults. Or just add fish! (See
below for information on managing bullfrogs.)
Repellents and scare devices do not work on frogs. No poisons
should ever be added to the water to keep these animals out.
The bullfrog (Rana catesbeiana, Fig. 8) has successfully
spread throughout the low elevations of Washington. Large populations
of this species are believed to have contributed both directly
and indirectly to the drastic decline of native amphibians and
The bullfrog is the largest true frog in North America. It can
measure 8 inches in length, leap up to 3 feet, and live nearly
ten years. Bullfrogs are occasionally seen crossing roads, even
during periods of dry weather, and may travel overland up to a
mile. This movement allows them to expand their range from the
source where they were introduced. The large number of eggs in
each egg mass laid by the females allows bullfrogs to quickly
establish themselves within a new territory.
Bullfrogs get their name from the bar-room mating call made by
the males. Juveniles and adults of both sexes emit a squeak just
prior to jumping into water when avoiding an intruder.
The original native range of bullfrogs was the eastern United
States, but they have been introduced to most of western North
America, from southern British Columbia to Baja California. Bullfrogs
were first introduced into Washington during the Great Depression
(early 1930s) to provide opportunities for frog hunting, food
(i.e., frog legs), and stock for frog farms, enterprises that
Bullfrogs thrive in the warm waters of natural and man-made ponds,
marshes, sloughs, reservoirs, and sluggish irrigation ditches
and streams. Bullfrogs tolerate polluted and muddy waters better
than do most native frogs, and may be found within cities in wetlands,
reservoirs, and stormwater ponds.
8. Bullfrogs are expanding their range as individuals
colonize suitable habitats—often using constructed stormwater
ponds as stepping-stones between natural wetlands. Bullfrogs
also spread to new habitats when released as unwanted pets and
after people share frog eggs with their neighbors, not knowing
the damage they can do. (Photo by Jim Pruske.)
In their northern
range and in cooler climates, bullfrogs persist only in year-round
bodies of water because they require two years to develop from
eggs into adult frogs. In their southern range and in warmer areas,
they have been known to fully metamorphose in one year and colonize
semi-permanent and seasonal ponds. (Such cases have been documented
by biologists in Oregon.)
Bullfrogs breed only after the nights warm up and reach the high
60s and 70s (Fahrenheit), generally June and July here in Washington.
Adult bullfrogs and tadpoles overwinter in mud on the bottom of
ponds and other bodies of water. They hibernate by burying themselves
in surface mud or by digging cave like holes underwater. Adults
also hibernate on land near ponds where they bury themselves within
the soil. Their body temperature may drop virtually to the freezing
point, and their hearts slow so drastically they seem to atop
altogether. But they continue to absorb oxygen through their moist
skin, and when their surroundings thaw, they emerge into the spring
sunshine to resume their business of catching insects and other
Adult bullfrogs usually are "sit and wait" predators
that readily attack almost any live animal smaller than themselves—insects,
frogs, tadpoles, fish, small snakes, turtle hatchlings, newts,
salamanders, bats, hummingbirds, and ducklings. Bullfrogs use
their sticky tongues to subdue prey, but that's not their
only method of securing food. Large frogs are more likely to lunge
at their targets. Once they get a grip with their wide, sturdy
jaws, they use their front feet to shove the items down their
Garter snakes regularly catch and eat bullfrog tadpoles and adults.
Painted turtles also eat some in late summer, when adult and developing
bullfrogs become sluggish for some unknown reason. Large bullfrogs
also capture smaller ones and eat them.
The relatively unpalatable nature of bullfrog tadpoles may give
them the ability to coexist with many otherwise potential fish
predators. Bullfrog eggs can be eaten by many predators (leeches,
salamanders, fish) with no obvious detrimental effects to the
Under no circumstances should you take or purchase bullfrog tadpoles
for your home pond, transfer wild-caught bullfrogs, or in any
way encourage them to expand their range. If you are adding plants
or water to a small pond, make sure you are not also adding bullfrog
eggs or tadpoles.
bullfrog creates one thin-jelly egg mass that may contain 6,000
to 20,000 very small eggs, which are black on top and white
underneath. Egg masses are generally found in water that is
less than 2 feet deep in mid to late summer. The eggs start
out as a round, basketball-size mass (below or near the surface)
that then rises, flattens out, and forms a 2- to 4-inch gelatinous
mass 2 feet in diameter. The egg mass floats on the surface
of the water or rests on the bottom within sparse vegetation.
The mass remains attached to deep vegetation in some places
and is often covered in algae.
9. Bullfrog tadpoles are dark green with black dots,
orange or bronze eyes, and opaque yellow underbellies.
(Photo by Russell Link.)
The tadpoles are dark green with black dots, orange or bronze
eyes, and opaque yellow underbellies (Fig. 9). A two-year-old
tadpole may be 4 to 6 inches long.
are green to brown with a peppering of tiny black spots, and
have orange or bronze eyes. A fold of skin extends from the
eye around the eardrum.
bullfrogs have thickset bodies, large, exposed eardrums, and
are green, tan, or dark brown above (with dark spots). Male
bullfrogs have a yellow throat. The eardrums on males are
larger than the eyes, while the female's eardrums are
the same size as the eyes. The eyes of both sexes are gold.
The removal of bullfrogs is unlikely to be a viable management
option in most wild or semi-wild situations owing to the difficulty
of removing all bullfrog eggs, tadpoles, and adults, and preventing
surrounding bullfrogs from invading the water body. However, in
a small wetland or pond it may be possible to eliminate the local
bullfrog population by visiting the pond daily through the breeding
season and removing all eggs, tadpoles, and adults. Long-term
success depends on closely monitoring the pond to prevent other
bullfrogs from breeding.
Bullfrog control techniques should be limited to those that cause
the least harm to native amphibians. At least one person should
be able to identify all stages of native amphibians when attempting
to manage bullfrog populations. Foot traffic in areas where many
juvenile toads, red-legged frogs, or other species are about should
Adult bullfrogs are difficult to gig or catch in nets because
they are very wary and leap for the water at first approach. However,
when they stare at a bright light at night, they seem unable to
see a hand, net, or frog gig reaching out to grab them. Wear a
headlamp to keep your hands free, or have someone next to you
spot the bullfrogs using a powerful flashlight. Some people have
found capturing adult bullfrogs in turtle hoop-nets to be a useful
Shooting adult bullfrogs using a single-shot 4/10 shotgun has
been successful. Alternatively, a pellet gun or a bolt-action
.22-caliber rim-fire rifle and dust-shot bullets can be used at
close range. Use only dust shot in the .22, not conventional ammunition.
Because all shot has the potential to ricochet, exercise extreme
caution when discharging firearms on or near water.
Because adult bullfrogs are less active in cooler water, usually
March and April are the best months for catching or shooting them.
Bullfrog tadpoles are equally difficult to catch because they
quickly swim to deeper water to avoid capture. However, capture
is made easier if the water body in which the tadpoles (and adults)
live and breed is lowered with a pump or by another means to make
them more accessible. Tadpoles are best captured using a long-handled
dip net (not a fish net).
Tadpole collection should be done when non-target species (especially
native amphibians) are unlikely to be caught. For instance, in
early September, when native frogs and salamanders occupying the
site have turned into their juvenile stage and the only tadpoles
left are bullfrog tadpoles.
Bullfrog eggs should be carefully collected in a large dip net
or a 5-gallon bucket to avoid breaking up the egg masses. Clipping
of vegetation may be necessary to dislodge the egg masses.
Euthanasia of adult bullfrogs and tadpoles can be by a blow to
the head or the two-stage process of refrigerating the animals
for an hour to slow down their respiratory system and then freezing
them. The same can be done for the eggs, or they can be left a
distance away from the water body to be eaten by a bird or other
Since bullfrogs generally require two years to develop, it may
be possible to rid an area of these animals by draining the water
body they inhabit. This assumes that there isn't another
nearby water body that can serve as temporary harborage. (Where
ponds have dried up naturally, adult bullfrogs have been known
to seek refuge in nearby wells, springs, animal burrows, and crevices
in the ground.)
The Northern leopard frog and Oregon spotted frog
are state endangered species (WAC
232-12-014) and cannot be hunted or trapped. All other species
of frogs are unclassified and can be controlled without a permit.
is classified as a prohibited aquatic animal species (WAC
220-12-090). No license is required to hunt bullfrogs, there
are no bag limits, and the season is open year round.
It is unlawful to import into the state, hold, possess, offer
for sale, sell, or release all frog species into the wild without
the proper license to do so (WAC
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Internet Center for Wildlife Damage Management