Head of Cane Toad showing pronounced angular ridge above the nostril. The schooling behaviour of Cane Toad tadpoles. A large Cane Toad showing large venom glands behind the ear and typically warty skin. A Freshwater Snake that died while attempting to eat a Cane Toad.
Cane Toads have tough, leathery skin with a distinctly warty appearance. They have a bony ridge above the nostril and a pronounced, venom-producing gland behind the ear. The back colour is variable but usually grey, brown, reddish-brown or yellow and the belly is white with grey mottling. This species obtains a large size, up to 26 cm and weighing 2.5 kg, but specimens of this size are rare.
Cane Toads are native to North, Central and South America and were introduced to Queensland to control cane beetles, important pests in the sugar industry. They were released in north Queensland in 1935 and now occupy an arc extending from the Yamba district of NSW to far north-western WA. Their present distribution covers around half of Queensland but is still expanding.
Cane Toads can colonise a wide range of habitats. They are found in open forests, grasslands, swamps, beach dunes, farmland and suburban areas. They are not widely spread through rainforests but will penetrate these areas along roads and walking tracks.
Cane Toads are often encountered on roads at night. They have an upright posture and move with short rapid hops. They are frequently found around outdoor lights that attract nocturnal insects.
Female Cane Toads lay their eggs in a long string of jelly and can produce as many 30,000 eggs in a season. The eggs are deposited on the bottom of ponds or pools of water. The eggs are tolerant to a wide range of conditions and will even develop in brackish water. The tadpoles hatch within 24–72 hours, they are small, black and numerous and form dense schools. The toadlets are around 1–1.5 cm when they leave the water and are often present in large numbers. Mortality is high for the young toads but those that survive grow quickly and reach sexual maturity within a year (in the tropics).
Male Cane Toads call with a continuous warble, not unlike the sound of a small petrol engine running.
A Cane Toad can be distinguished from all native frogs by its extremely warty skin, large venom-producing gland behind the ear and distinctly mottled belly.
Cane Toads produce a cocktail of highly-toxic, physiologically active substances. These substances are concentrated in their 'warty' skin and are secreted by two large parotoid glands behind the ears. Toxins are also present in the body tissues, toad eggs and tadpoles. Cane Toads are inoffensive when left alone, but their toxins are very dangerous if eaten or rubbed into the skin or the eyes.
Impact on (Australian/our) native wildlife
Because of their toxic nature, Cane Toads are a serious threat to our native wildlife – particularly animals that feed on frogs. Marked declines have been observed in some snake and goanna populations following the invasion of Cane Toads into an area and, undoubtedly, toads have caused the local extinctions of some of their predators. Additionally, toads compete with native species for sheltering sites and food resources. While they feed primarily on insects, they are opportunists and will also take small vertebrates.
A handful of native animals can eat Cane Toads and survive. Amongst these are the Snapping Turtle, Wollumbinia latisternum; the Freshwater Snake, Tropidonophis mairii; the saltwater crocodile, Crocodylus porosus; the Water Rat, Hydromys chrysogaster; and some birds such as ibises and the Torresian Crow, Corrus orru.
The full impact of Cane Toads on our wildlife may never be fully appreciated. They have spread rapidly from their release points and continue to advance south and west across Australia. It is difficult to separate their impact from that caused by human population growth: the clearing and degradation of native vegetation, waterway pollution and the spread of introduced plant and other animal pests.
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