The Cane Toad Disaster • Vol. 19: #16 • (4-9-2023) Tidbits of Coachella Valley

• In the 1930s, farmers in Australia were worried about their sugar cane crop, which was being ravaged by the cane beetle. To solve the problem, they imported 102 cane toads from Hawaii. The toads were kept in an enclosure to breed.

• In 1935, 2,400 cane toads were released into the sugar cane fields of Queensland, Australia, with the hope they would save the sugar cane crop from the cane beetle. It turned out to be an ecological disaster of unprecedented proportion.

Workers in Australia's sugar cane fields, in the 1930s.

• For one thing, and for several reasons, cane toads do not eat cane beetles. First of all, cane beetles are active during the day (cane toads are nocturnal), and cane beetles also live either under the soil (the toads do not dig) or in the leaves (toads don’t jump very high). Adult beetles fly away (toads don’t fly), and cane beetles prefer bare ground (toads prefer ground cover).

• For another thing, there are no natural predators to control cane toad numbers. In addition, they are poisonous. And finally, they breed prolifically.

• Each toad has poison glands on its shoulders which can shoot a milky white neurotoxin up to three feet. In their native Central and South America, predators that live alongside the cane toad, such as the caiman, have natural defenses against the toxin that the cane toad secretes. Australia’s native species are not equipped to defend themselves in this way. A single lick or bite causes native animals to experience rapid heartbeat, excessive salivation, convulsions, paralysis, and ultimately death when the heart stops.

• It’s not only the adults that are poisonous. Even the eggs and the tadpoles are toxic.

• Other species of frogs and toads lay perhaps 1,000 eggs at a time, hoping that one or two will survive. The cane toad lays up to 30,000 eggs at a time, and because no creature in Australia can eat those eggs, they all hatch.

• Meanwhile, the tadpoles, and then the voraciously omnivorous adult cane toads, eat all available foods that other creatures depend on, while poisoning everything that tries to eat it, and simultaneously devouring entire populations of frogs, lizards, bugs, and snakes.

• The cane toad is large, growing up to nine inches in length, and can easily swallow creatures such as birds and mice. A small marsupial called the Northern quoll has been brought to the brink of extinction. Fresh water crocodiles are experiencing record die-offs after eating the toad. Various species of snake have suffered as well. Turtles and fish that eat the poisonous eggs and tadpoles also die. The cane toad is a singlespecies ecological wrecking ball.

• Making things worse, cane toads inhabit a wide range of ecological niches including rainforests, coastal mangroves, sand dunes, shrubs, and woodlands. They don’t need much water to reproduce; anything from a puddle to a river is fine. They can survive cold temperatures that kill other amphibians. They begin mating at the age of one year, and can continue to mate for nearly 20 years.

Map of Australia, showing sustainability of precipitation for Cane Toads.

• By 1945, a pesticide had been developed that controlled the cane beetles. By then the cane toad was on the march across the entire continent of Australia, expanding their territory at a rate of up to 40 miles per year.

• However, there is hope. Water rats learned that if they flip the toad on its back, they can avoid the poison. Birds learned that if they harass the toad by flipping it into the air numerous times, and then rinse it in water, they can eat it without harm after it has expended its stores of toxin.

• Because the toad outpaces the available supply of food, cane toads are now eating smaller cane toads, and larger tadpoles are eating smaller tadpoles. Furthermore, scientists are working to release genetically modified male cane toads that can only have male offspring. □