The cane toad is a large and highly toxic amphibian. It’s considered one of the world’s most destructive invasive species after being introduced to countries across the globe as a biological control against insect ‘pests’ on sugar-cane crops, hence its common name. These introductions were largely unsuccessful, particularly in Australia.
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Find out everything you need to know about the cane toad.
What is the cane toad’s natural habitat?
These terrestrial, nocturnal toads are native to South and Central America. They are adaptable and inhabit a variety of humid habitats, including grasslands, woodlands, wetlands and agricultural areas. They also live in urban areas, roadsides and gardens. The toads are attracted to places where there is standing water for egg-laying.
How does a cane toad produce toxin?
Cane toads have glands on their shoulders, known as parotoid glands. These release a milky-white toxin (known as bufotoxin) when a toad feels threatened. According to the Australian government, if cane toad toxin is ingested by other animals, it affects the heart, can cause excessive salivation, convulsions and paralysis, and result in death. The amphibians are toxic at all life stages – eggs, tadpoles, toadlets and adults.
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Can any animals eat cane toads?
Predation on these amphibians remains limited, as many animals succumb to the toads’ toxins. However, some species have adapted to prey on cane toads without being harmed, either by avoiding the poisonous parts or being naturally resistant to the toxins.
The Australian Museum reports that the keelback snake can eat cane toads without lethal effects, and that red-bellied black snakes living in areas where cane toads are abundant have developed a higher resistance to the toxins, or avoid eating the toads altogether. Crows have learned to flip cane toads onto their backs to eat their non-poisonous bellies. Ibis wash cane toads before eating them and water rats remove parts of the toad that are safe to eat, such as the heart.
So, what happened in Australia?
In 1935, cane toads were introduced to Queensland to control two species of sugar-cane beetle, whose larvae eat the plant’s roots. The results were disastrous. Cane toads are prolific breeders, and managed to rapidly expand their own population while failing to control that of the beetles. They caused significant ecological damage, outcompeting native species and consuming and poisoning the beetles’ natural predators. Their presence is also thought to have increased the abundance of crop-eating rodents that can consume toads without ill-effect.
How many cane toads survive in Australia today?
There are reportedly more than 200 million cane toads in Australia. Since its introduction in 1935, the species has spread into most of Queensland, west through the Northern Territory into Western Australia, and south into New South Wales. Initiatives such as the Great Cane Toad Bust, which encourages participants to catch and humanely kill the amphibians, are attempting to curb numbers.
What’s the largest cane toad recorded?
The Guinness World Record for largest toad dates back to March 1991, with a pet cane toad named Prinsen (The Prince) who weighed 2.65kg. However, another huge individual was found by rangers in Queensland’s Conway National Park in January 2023. Nicknamed ‘Toadzilla’, it tipped the scales at 2.7kg, appearing to beat Prinsen’s record. As is standard practice, Toadzilla was humanely euthanised.
What do cane toads eat?
Cane toads are opportunistic feeders with a varied diet. They primarily eat invertebrates, such as ants, termites, beetles, snails, spiders and grasshoppers, but also consume small reptiles, amphibians and even small mammals and birds if they can catch them. Cane toads are also scavengers, consuming carrion and food left out for pets. Instead of drinking, the toads absorb water through the skin on their bellies.
How many species of cane toad are there?
The United States Geological Survey (USGS) states: “Cane toads have long been considered to be one species throughout their range. However, studies have now differentiated these cane toads into two species: [the South American cane toad] Rhinella marina, found in South America east of the Andes, and [the Mesoamerican cane toad] R. horribilis, from South America west of the Andes through Central America to Texas.” The former is the species that has been introduced widely worldwide. Both species are listed as Least Concern by the IUCN and have increasing populations.
How do cane toads breed?
Cane toads can breed all year round. Following amplexus (eggs are fertilised externally), spawn occur in long gelatinous rows of black eggs in the slow or still shallow waters of ponds, ditches, temporary pools, reservoirs, canals and streams. The clutch size can be between 8,000 and 17,000 eggs (clutch sizes of 35,000 are also known). Cane toads reach sexual maturity between 6 and 18 months and have a lifespan of about five years.
Cane toads at a glance
- Scientific family name: Bufonidae
- Average lifespan: 5 years in the wild
- Length: 10 to 15cm
- Weight: 1.5kg
Main image: close up of a cane toad/Getty
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