FASCINATING
FROGS
An excerpt from ‘Wetland Warbler’, the newsletter of the Friends of
Edithvale-Seaford Wetlands Inc (No. 55, February 1999).
There are nine different species of frogs which
occur in the southern suburbs of Melbourne. All of these, as tadpoles, require
water in which to develop, even those species which spawn and possibly live on
land. Frogs’ eggs are usually referred to as egg masses or spawn.
The life cycle of a frog may be divided into
several stages: eggs, tadpoles, 'metamorphlings' and adults. Most tadpoles
hatch after a few days, but some terrestrial (land) eggs may remain unhatched
for nearly six months waiting to be flooded by water.
Adult frogs are easier to identify than
immature stages. The most conspicuous feature of most species, is the male
advertisement call, used during the breeding season to attract females. To
maintain a stable population, each adult needs to produce only one successful
offspring in its life. However, a great many frog species have been reported to
be in decline. The significance of that statement becomes clear when we
consider that some species lay upwards of 50,000 eggs in a lifetime!
Next time you visit the wetlands bring this
article and see if you can identify any frogs you see or hear.
1. GROWLING GRASS FROG Litoria
raniformis
Adults are bright emerald to dull olive green
with brown and/or gold blotches on a warty back. The call is a growl of about 1
second long - "crawark-crawark-crok-crok" - repeated every few
seconds and they call from August to April. They lay eggs in October. Warning
- these frogs may have strong toxins on their skin to protect themselves which
may be irritable or harmful to humans. Wash hands after handling; do not touch
your eyes or mouth.
2. SOUTHERN BROWN (EWING’S) TREE FROG Litoria
ewingi
Adults are pale fawn with cream, orange or
light brown sides. An agile climber and jumper. Call is a series of rapid
harsh, whirring, pulsing notes repeated 5 to 15 times, the first note usually
the longest, "creeeeee creee creee creee creee creee", heard year
round. Eggs and tadpoles can be found all year except January.
3. WHISTLING (VERREAUX’S) TREE FROG Litoria
verreauxi
A clumsy climber, fair jumper, but strong
swimmer. A fawn coloured frog with dark or black patches on the sides and in
the groin. The call is a rapidly repeated burst of 10-20 short notes with an
almost whistling quality – "tweee tweee tweee twee twee…" and can be
heard year round. Eggs can be found in August, October, November and March.
4. VICTORIAN SMOOTH FROGLET Geocrinia
victoriana
A darkish brown frog marbled with pink on
hind of thighs, smooth bellies and sometimes a pink patch in armpits or groin.
Call is most distinctive, a long harsh introductory note followed by a long
series of short rapidly repeated explosive musical notes "wa-a-a-a-a-ark
pip-pip-pip-pip-pip-pip..." heard from September to June. Eggs can be
found from December to January and tadpoles in November, December and March.
5. POBBLEBONK (BANJO) FROG Limnodynastes
dumerili
This burrowing frog is mainly dark in colour
- a mixture of dark medium and light browns with either a smooth white or
mottled belly. The call is a short musical, explosive note producing a resonant
"bonk" reminiscent of a banjo, usually repeated every few seconds and
can be heard all months except July. Eggs are found from August to April and
tadpoles all year round
6. SPOTTED MARSH FROG Limnodynastes
tasmaniensis
One of Victoria’s most common frogs, it is
fawn with large regularly-shaped olive green/brown blotches on its back,
sometimes with a yellow, red or orange stripe down the centre of its back. They
call all year except June with the call being a short, sharp "click"
or "plock" similar to the sound of two stones being struck together.
Eggs are found all months except June, July and March and tadpoles year round.
7. STRIPED MARSH FROG Limnodynastes
peroni
Adults are voracious hunters and may eat
other smaller frogs and range in colour from pale fawn to golden brown with
dark brown or black stripes running down its back. With similar inflections to
a hen’s cluck, the call is a single short soft explosive note (similar to the
spotted marsh frog). "Tock" or "poc" can be heard all year
except July and eggs can be discovered in August, September, December and
January. Tadpoles occur all year long.
8. COMMON SPADE FOOT TOAD Neobatrachus
sudelli
Found in drier areas, this one is a burrower
and remains buried, becoming active after rains. Another dark coloured frog
with a distinctive vertical pupil, it has a ‘baggy-pants’ look as the groin
skin is loose. The call duration is 1 to 2 seconds, a slowly pulsed musical
trill - craa-aw-aw-aw-aw-aw-aw-awk" - heard all year round except December
and January. Eggs occur from April till July.
9. COMMON FROGLET Ranidella signifera
Often called the Ratchet Frog (say that very
carefully!) because of its insistent call, this last south-suburban frog is
variable in back colour and patterning. All are dark fawn to mid-brown: 1 with
longitudinal ridges, 1 with boomerang-shaped ridges over shoulder and on back
and 1 with back smooth, unpatterned or with small warts. The call is a series
of three to five short pulsed calls with a cricket-like chirping quality,
rapidly repeated in a long series - "crick~rick-cnck-crick-crick" -
heard year round. Tadpoles are found in October to December, with eggs found
from July to November and then again in February.
PLEASE NOTE:
The Wildlife Act 1975 protects all native
wildlife (including tadpoles and frogs) alive or dead. It is an offence to be
in possession of any wildlife without a valid licence or permit, which as a
rule are only granted to research institutions or wildlife study groups and
individuals affiliated with them.
Further information on licenses and permits
can be obtained from the Department of Natural Resources and Environment
(DNRE).
Further Reading:
Frogwatch - Field Guide to Victorian Frogs by Hero, Little john and Marantelli, 1991.
Publishers: DNRE Information Centre, Melbourne (The information for this
article came from the above book, but it contains much, much more.).
Australian Frogs by M.J. Tyler, 1989. Viking O'Neil Penguin, Ringwood
The Cold-Blooded Australians by G. Schmide, 1985. Doubleday Australia.
Frog Call Tapes:
If you would like to purchase a good quality,
home-made recording of the frogs as listed in this article, please contact Kaye
Proudley on 9580 3341 to order your copy. The cost is $6 dollars with all
profits going to Friends of Edithvale-Seaford Wetlands Inc.
FROGS
& DRUGS
An excerpt from ‘Wetland
Warbler’(No. 55, February 1999).
Due to a resurgence of interest in so-called
alternative medicines, frogs and toads have come into special focus because
they have a wide array of compounds of clinical interest in their skins. In
fact, their skins are more complex than that of any other type of living
creature. There may be 20 or 30 chemical compounds in a single species and
every species seems to have some chemicals not possessed by others.
Whilst not all frog and toad secretions are
toxic, some are – so virulent that they beat the most venomous snake hands down
and have been described as the most toxic substance known to mankind.
In 1757 it was written that an amorous women
of Rome, (married to an invalid husband with a weak heart and fluid retention)
wishing to hasten her husband’s death, made a potion from a toad and slipped it
into his drink. But she made a fundamental error in the identification of the
toad species. The one she selected contained a heart stimulant and a diuretic
which increased his flow of urine. Result? She cured the husband she detested
and restored him to perfect health!
A compound has been found in the skin of the
Green Tree Frog (Litoria caerulea) of northern Australia and named Caerulein in
the frog’s honor. It is marketed in Germany and was initially tested as a drug
to reduce high blood pressure, but was found to be a powerful stimulant of the
gut and is now used following major abdominal surgery.
It has also been put to use in the human
brain with symptoms of chronic schizophrenia being blocked for a month
following one injection.
Michael Tyler has discovered a creamy
secretion exuding from a head gland of the Magnificent Tree Frog and after
testing the extract of cultures on bacteria, fungi and viruses, has
demonstrated their ability to inhibit the growth of the virulent Golden Staph
(Staphylococcus aureus) and the virus Herpes simplex. However, because the
crude secretions were a cocktail of as many as 30 chemicals and the testing results
were not always the same when tested on living mammalian cells, and when each
chemical was separated and some tested separately (at a cost of $2,000 to
$3,000 for just 10mg for each chemical) it seems the expense will kill the
ideas in the bud. Without the support of major drug companies, the testing and
findings will not be exploited and brought to the pharmacy shelf.
In many countries including Australia people
are alarmed at the decline and disappearance of frog populations. The discovery
that frogs are mobile pharmacies may just provide the stimulus to assist their
survival.
(Condensed from an article by Michael
Tyler, published in Australian Natural History, Vol. 34, No. 12, 1995).
Thanks to Kaye Proudley from the
Friends of Edithvale-Seaford Wetlands Inc. for allowing the MBCL to reproduce
these excerpts on the MBCL web site.