The cane toad ( Rhinella marina ) has been identified as the world’s most invasive species , symbolising the global ecological risks associated with the relocation of wildlife across ecosystems. Originally native to South and Central America , the cane toad was deliberately introduced to several countries to control agricultural pests, but the plan backfired dramatically. Instead of reducing pests, the toads multiplied uncontrollably, causing deep and long-lasting ecological disruptions.

Origins and Accidental Spread

In the 20th century, cane toads were released in Australia, the Caribbean and multiple Pacific Islands to combat beetles damaging sugar-cane crops. The biological-control experiment proved ineffective. The beetles remained unaffected, while the cane toad quickly established itself due to its remarkable adaptability and absence of natural predators in new environments.

Physical Features and Toxic Defence Mechanisms

Adult cane toads typically range from 10 to 20 centimetres , though some individuals grow even larger. Their warty skin and large parotoid glands enable them to secrete potent bufotoxins , which can fatally poison animals with no natural resistance. Even juveniles carry enough toxins to deter many predators, contributing to rapid population expansion.

Invasive Traits and Adaptability

Cane toads thrive in diverse conditions—extreme heat, cold, drought and disturbed human habitats. Studies show that toads at the invasive front evolve longer limbs and greater endurance , accelerating their spread. They establish themselves easily in wetlands, farms, suburban gardens and modified landscapes, showcasing exceptional ecological resilience.

Global Ecological Impact

Cane toads prey on insects, small mammals, reptiles and even carrion. Their presence disrupts food webs, decimates predator populations (notably in Australia) and competes heavily with native amphibians. Their high reproductive rate and environmental tolerance make long-term containment extremely difficult.

Exam Points

• Scientific name: Rhinella marina .

• Introduced for pest control; became highly invasive instead.

• Produces bufotoxins from parotoid glands.

• Extremely adaptable to heat, cold and dehydration.

• Causes predator declines and major ecological imbalance.

• Established across Australia, the Caribbean and Pacific islands .