The cane toad (Rhinella marina), introduced to Australia in 1935 to control sugar cane beetles, failed in its intended purpose but has since become a highly successful invasive species across the continent’s north and east. This large amphibian is known for its prolific breeding and potent toxins. Its remarkable spread is directly linked to an extremely flexible and opportunistic diet, which has profound consequences for native wildlife and ecosystem function.
Generalist and Opportunistic Feeding Habits
The adult cane toad is a generalized predator, meaning it is not selective about the food it consumes. Its feeding strategy is opportunistic, relying on the availability of prey in its immediate environment. Cane toads are nocturnal hunters, becoming active after sunset. They rely heavily on visual cues, detecting movement to snap up anything small enough to fit into their wide mouths. This non-selective approach allows them to rapidly exploit localized food sources in varied Australian habitats.
Primary Adult Food Sources
The bulk of the adult cane toad’s diet is composed of terrestrial invertebrates, including a vast array of Australian species. Scientific analysis of stomach contents frequently shows that ants, termites, and beetles are the most numerically important prey items. The toads often congregate near sources of these insects, such as termite mounds or areas with high ant activity. Beyond native insects, cane toads are sustained by non-natural food sources, particularly in areas near human habitation. They readily consume pet food left outside and scavenge on carrion, discarded food scraps, and other organic refuse, demonstrating their extreme adaptability as omnivores.
Diet Variation Across Life Stages
The diet of the cane toad changes significantly as it progresses through its various life stages, starting in the aquatic environment. Cane toad tadpoles are primarily detritus, algae, and suspension feeders, using their specialized mouthparts to filter organic sediment from the water column. They thrive in still or slow-moving water bodies where they are laid. A unique aspect of the tadpole diet is cannibalism, where the larvae will actively prey upon cane toad eggs and smaller, younger tadpoles. Once metamorphosis is complete, the tiny toadlets transition to a fully terrestrial diet focused on small insects, which expands in size and variety as they grow into large adults.
Ecological Impact of Cane Toad Predation
The sheer volume of food consumed and high population densities create significant ecological pressure on native insectivores. Cane toads directly compete with native species like small mammals and reptiles for primary food sources, leading to a decline in invertebrate abundance in colonized areas. This resource depletion stresses populations of native predators that rely on the same insects. Adult toads also prey on small native vertebrates, including lizards, small frogs, and snake hatchlings. This direct predation, combined with the lethal poisoning of larger predators that attempt to eat the toxic toads, causes a dual-impact on native fauna.