APPEARANCE
The cane toad (Bufo marinus), also called giant toad or marine toad, is typically toad-like in shape,
but compared to the type you might find hopping around your back yard, is like a toad on steroids.
It's a giant among toads. The largest specimen on record weighed almost 6 pounds and measured 15 inches
from snout to vent (external opening of the cloaca). Adults average about a foot (30cm) long, making it one
of the largest amphibians.
The rough warty skin comes in a range of colors from gray, brown, red-brown or olive, with varying patterns.
A large bulge behind each eye marks the location of large parotoid glands, which produce venom that deters
opportunistic predators. When threatened, the toad secretes a toxic milky substance from the parotoid glands.
The secretion should be avoided, as it will burn eyes and inflame the skin. It can kill cats and dogs that
ingest it.
The toad's underside (ventral surface) is yellowish-white, usually blotched black or brown. Like most
other toads, the pupils of the eye are horizontal. The irises of the eye are bright yellow. The legs are
stubby while the rear foot's toes are webbed at their base, while the front leg toes are not webbed.
HABITAT AND DISTRIBUTION
Unlike many other amphibians, the cane toad's numbers are going up, not down. Originally native to
Amazonia, it is established in now colonizing southern parts of the US and Australia and is a serious pest in
places. They adapt well to human habitation, thriving in developed areas. Artificial ponds and waterways are
ideal for spawning whereas electric lights attract abundant insect prey upon which the toads feed—cane
toad convenience food.
FEEDING AND DIET
The cane toad is an ambush predator, its staple diet is invertebrates such as grasshoppers, caterpillars,
and ants, together with millipedes and snails. However, they are voracious predators and will prey on birds,
reptiles and even small mammals—anything they can swallow. One scientist wrote that cane toads would
eat "almost any terrestrial animal." Near inhabited areas, it has been known to cause the death of
pets that attack it due to the powerful skin toxins.
BREEDING
Cane toads breed year round in undisturbed water, streams, canals and ditches but are not deterred by human
presence or activity. The male calls to attract females. His call is a high pitched 'brrrr' that resembles the
a cell phone's dial tone.
As their eggs and tadpoles are poisonous, few predators will attack the juvenile stages, enabling the toad to
increase rapidly in numbers. In the wild, individual toads are thought to breed for at least five years,
while in captivity toads can live 15 years or more. Fertilization is external. As the female extrudes long
double chains of black eggs enclosed in a transparent cover, the male fertilizes them. In an single spawning,
a large female can lay up to 20,000 eggs.
The tadpoles are black above and silvery white with black spots below. They reach up to 1 inch (2.5 cm) and
are gregarious, forming large shoals that patrol the pond or puddle.
CONSERVATION
In Amazonia, and some areas where they are introduced, cane toads are beneficial predators, consuming vast
numbers of insects that would otherwise need to be controlled with pesticides. Elsewhere, however, the cane
toad itself causes conservation problems.
In areas where it has established, it can threaten native species that are not adapted to defend themselves.
Even predators are at risk, since the toad's skin toxins can kill unwary attackers. The Invasive Species
Specialist Group has nominated the cane toad as among the top 100 of the "World's Worst"
invasive species.
Scientists have advocated biological control to control numbers and limit the spread of the cane toad.
However, given the ease with which they adapt to human presence and are transported in shipments of fruit and
other commodities, biological control may prove ineffective. Until suitable methods are developed, the best
way to control cane toads will be to impose quarantine checks and to eliminate any toads accidentally released.
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