The Australian Cane Toad
THE AUSTRALIAN CANE TOAD
The cane toad, Bufo marinus, or giant toad, was introduced to Australia by the sugar cane industry with government sanction, in order to control two specific pests of sugar cane. The grey backed cane beetle and the frenchie beetle. Native to Central and South America, the cane toad has been introduced to several Pacific islands as well. One hundred and one toads arrived at Edmonton in North Queensland in June 1935. About 11 sugar growing locations in northern and central coastal Queensland received authorized shipments. People at Normanton and Burketown, and in northern New South Wales deliberately released the cane toad into the wild. Scientists warned the farmers not to bring the cane toad to Australia but the farmers did not listen and brought them in anyway.
Did the cane toad have any impact on the two cane beetles it was introduced to control? Apparently not. The cane toad ate beetles when they were available, but as a control agent, it had no impact at all. Instead of controlling certain insect populations, the cane toad ate large numbers of bees and other beneficial insects. Within 5 years, an effective insecticide became available and the sugar industry lost interest in the cane toad.
Although not native to Australia, the cane toad has one of the widest ranges of any living toad. The species lives in a wide variety of habitats, but is restricted mainly by the availability of water, since water is a vital element in the breeding cycle. However, toads can survive near very small pools, or steams in arid regions. During the dry or cold seasons, they remain inactive in shallow ground excavations beneath ground cover.
Cane toads are very large and heavily built amphibians (up to 15 cm long) with warty skin. The skin is strong, tough, and durable. Females tend to be larger and smoother-skinned than males. Cane toads are olive-brown to reddish-brown on top, with a paler white or yellowish belly. The underside is usually spotted with brown. The toad is characterized by a stout body, which is heavier than that of frogs.
The most distinctive features of the cane toads are bony ridges over each eye and a pair of enlarged glands, one on each shoulder. These glands are able to ooze venom. A pronounced angular ridge runs between the eyes and snout.
Giant toads can tolerate temperatures of 0 degrees Celsius to 41 degrees Celsius and are able to survive high levels of dehydration. They can also adapt to different temperatures. Their temperature and moisture tolerances may limit their distribution. However, they do occur in warm temperate to semi-arid climates and are abundant in the wet and dry tropics. A prediction, based on their ability to tolerate a variety of climates, is that they will become established in Darwin early next century and eventually spread over much of the coastal seaboard of Australia.
The call of the male cane toad is a high-pitched brrrr which sounds like a telephone dial tone. The cane toad also has a distinctive stance and hop. It sits upright in an almost vertical position and moves in a series of fast, short hops rather than long 'frog like' hops. Also cane toads do not have webs between their toes.
Cane toads will eat almost any small creature they can catch. They eat whatever is available. They often eat bees and dung beetles, small amphibians, reptiles, and mammals. In fact, they eat any animal they can swallow. Unlike other amphibians, giant toads eat things which do not move. They have also been known to steal food from dog and cat bowls.
They have few predators native to Australia. The common Fresh Water Snake, (Tropidonophis mairii), is the only Australian snake known to be able to feed on small cane toads without dying as a result. Other native animals such as the estuarine crocodile, the water rat and species of ibis are believed to feed on toads or on their internal organs.
Behavior and Breeding
Cane toads are highly adaptable, both in terms of survival and reproduction. They are much more tolerant than other Australian frogs and can survive and breed in somewhat salty water. In Australia, giant toads normally