Cane Toads - Bufo marinus
Cane
Toads are very large and heavily built
amphibians (up to 15 cm long) with warty
skin.
Females tend to be larger and smoother-
skinned than
males. They are olive-brown to reddish-brown on top, with a paler white or yellowish belly. The underside is usually flecked with brown.
Their most distinctive
features are
bony ridges over each
eye and a pair of enlarged
glands, one on each
shoulder. These
glands ooze Cane Toad
venom.
The
call of the
male Toad is a high-pitched "brrrr" which sounds like a
telephone dial tone.
They were introduced to
Australia in 1935 at Gordonvale, North
Queensland. Since then they have expanded their range to include about half of
Queensland. They have spread to the
Northern Territory and
New South Wales, and there are fears that they may soon colonise areas of the
Kakadu National Park. Occasionally individuals have shown up as far south as
Sydney. It appears that these have been carried south, in
plants for example, and there is no evidence of a
breeding population here.
Like all
frogs, they are primarily
insect feeders. However, they will attack anything that moves and is small enough to fit in their
mouths. Their
diet includes small
lizards,
frogs,
mice and even younger Cane Toads. They have also been known to steal
food from
dog and
cat bowls.
They are highly
adaptable, both in terms of
survival and
reproduction. They are much more tolerant than other Australian
frogs of variations in
water salt content, and can survive and breed in
brackish water.
Because their
diet is so
variable, they don't need to expend much
energy searching for
food. They can just sit in a convenient spot, and
gobble up anything that wanders by. In
urban areas, they are often seen gathered around
street lights eating
insects attracted by the
light.
They need only a small
pool of
water for
breeding. A
female toad can produce vast quantities of
eggs, up to thirty thousand a
month. The
males
fertilise the
eggs as they are laid in long strands.
Males will attempt to
mate with anything resembling a
female toad -
living or
dead.
In three days the
eggs
hatch into small (3 cm) jet black
tadpoles - unlike those of any
native frog. These
tadpoles become toadlets unusually early, so they are out of the water and hopping around faster than most other
frogs.
One of the most important factors in the
success of the Cane Toad is that they are highly
poisonous to eat, at every stage of their life cycle.
All
frogs and
toads may have enlarged
chemical-secreting glands at particular points on their
bodies, of small
glands spread over the whole
skin. The
chemicals they produce are highly varied, and in some cases may be highly
toxic. The Cane Toad is one such
amphibian. A Cane Toad's reaction to a threat is to turn side-on to its attacker so that the
venom glands face them. Cane Toad
venom is also found all over their
skin.
Animals picking up a Cane Toad and receiving a
dose of
venom may
die within fifteen minutes.
The glands on the Cane Toads'
shoulders are also capable of
oozing venom or even
squirting it over a distance of up to 2m if the
toad is particularly roughly treated. The biggest
danger to
humans is that the
venom could come in contact with the
eyes, where it causes intense
pain and temporary
blindness.
If handling a Cane Toad, it is important to wash your
hands immediately afterwards and to be careful not to touch your
eyes. If any venom does affect the eyes, bathing in running
water will relieve the
pain. Never
eat a Cane Toad, its
eggs or its
tadpoles.
Ecology
There is still much work to be done to fully understand what effects Cane Toads have on
native wildlife, and just how far they can spread. There are some reasons for optimism. In the areas where Cane Toads have been around for the longest time, their
populations have declined after the initial
population explosion. It is also possible that some
native animals are learning to avoid eating them. Other animals have shown they can eat the toad. The
Keelback Snake can
detoxify the
venom and
Water Rats,
Ibis,
Crows and some other
birds turn the toads over and eat only the non-poisonous internal
organs.