Australian National Botanic Gardens
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Australian National Botanic Gardens
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There are over 200 species of frog occurring in Australia. Frogs belong to the Class Amphibia, and all are reliant on moisture to breathe, reproduce and generally survive and thrive. Nocturnal life is one way of minimising the risk of drying out, for it is the coolest part of the day. Most frogs are active at night. Despite this drawback of a dependence on water, frogs have evolved and diversified in form to occupy a variety of habitats, from rainforests to deserts, from rock faces to subterranean burrows, from free water to sphagnum moss bogs - frogs are found in a surprising number of different spots.
Most frogs breed seasonally when conditions of temperature, day-length and moisture are right. It is common to see tadpoles (the name given to very young frogs) swimming in ponds at different times of the year. When a female lays eggs the male fertilizes them and the resulting floating mass of eggs (spawn) is left while the frogs develop. Hatching of the tadpoles may take several days, followed by a period when the tadpole develops and finally changes into the adult frog, a process called metamorphosis.
Frogs eat insects and overall must account for millions of insects daily. They also eat other small invertebrates. By eradicating millions of insect pest species frogs play an important role in maintaining the balance of nature. But something is happening to the environment, both within Australia and internationally, that is alien to frogs. In the past 15 years or so frog populations have declined dramatically, even in supposedly uncontaminated environments such as national parks. Something in the environment is killing the world's frogs. If we accept that frogs are indicator species and this is a warning that environmental changes are taking place, it is in our own interests to take heed of this potential tragedy.
Several species of frog can still be found, or, more likely heard, in the Australian National Botanic Gardens. At certain times of the year male frogs distend their vocal sacs (situated just below the throat) with air to serve as a resonance chamber to amplify sounds and issue a great variety of calls to attract females. It is common to hear great choruses of different species trilling away, endeavouring to attract mates. Frogs which can be heard in the Gardens, in decreasing order of likelihood of discovery, are:
Common
Eastern Froglet - Crinia signiferaA small frog up to 3 cm in size. Extremely variable in colour and pattern.
Upper surface pattern of either uniform light grey or brown contrasting
with black sides; or grey or brown with irregular darker patches and sometimes
a light vertebral stripe; or a broad dark vertebral band bordered on either
side by a light brown or grey band from eye to groin. This small gregarious
species is common in and around the pools in the Gardens.
Call: "crick-crick-crick"
Embedded sound MP3
Eastern
Banjo Frog - Limnodynastes dumeriliiA stout frog from 6-8 cm in size. Grey or brown with blackish marblings,
with or without a continuous or broken narrow vertebral stripe. Sides often
beautifully marked with a bronze and purple sheen with black mottling.
A pale yellow stripe from below the eye to above the base of the forelimb
is conspicuous. Common in ponds around the Gardens.
Call: "bonk-bonk-bonk". Two or more frogs in unison
sound like "pobblebonk"
Embedded sound MP3
Spotted
Grass Frog - Limnodynastes tasmaniensisUp to 4.5 cm in size. Light brown to rich olive-green above, usually
with a series of large, regular dark brown splotches and often with a narrow
white, yellow or russet vertebral stripe from snout to vent. Shelters under
logs and stones on edges of permanent and temporary swamps, pools and creeks.
Call: a very rapid "uk-uk-uk-uk"
Embedded sound MP3
Brown-striped
Frog - Limnodynastes peroniiUp to 6.5 cm in size. Light brown above with a series of irregular dark
brown stripes. Frequently a pale vertebral stripe from snout to vent. A
dark brown band behind eye. Secretive by day, hiding under logs, stones
or leaf litter. Burrows effectively.
Call: usually a single "plonk" or "whuck",
repeated at intervals of a few seconds.
Embedded sound MP3
Peron's
Tree Frog - Litoria peroniiMedium-sized frog to 6 cm. Rich grey or brown above, varying in intensity
with temperature and temperament. Irregular darker mottling and numerous
small bright green spots over upper surface. Groin and hind sides of thighs
mottled black and bright yellow. May be found long distances from water
in a variety of habitats, usually in trees and shrubs. Will forage for
food on the ground.
Call: a loud, penetrating long rattle. Has been variously described
as a "loud chuckling trill" and a "sound of a pneumatic
drill"
Embedded sound MP3
Eastern
Froglet - Crinia parinsigniferaSmall frog to 3 cm in size. Almost indistinguishable from the Common
Eastern Froglet. Males may only be distinguished by their call. Females
have a rather granular white belly pattern while Common Eastern Froglet
females have a belly mottled with black and white. Difficult to find this
species in the Gardens, although it is present. More experienced observers
may pick it out by the different call.
Call: long, low drawn out "squelch".
Embedded sound MP3
Whistling
Tree Frog - Litoria verreauxiiUp to 4 cm in size. Highly variable in colour pattern, this species
may be fawn, brown or reddish-brown above. A dark brown stripe extends
from the nostril through the eye to the shoulder. Groin pale yellow with
black spots. Front and hind sides of thighs are orange. Found in a variety
of habitats from swamps, lagoons, wet and dry sclerophyll forest to alpine
grassland and bogs. Breeding groups occur around ponds, dams and creeks.
One of the few species to call throughout the year.
Call: rapid, pulsing whistle "cree-cree-cree-cree".
Embedded sound MP3
Written by Ric Longmore
Sound recording by Ric Longmore
MP3 sound conversions by Graham Ranft
Illustrations by Donna Wahl
Note: drawings are not to scale.
Adapted for the Internet by Murray Fagg