Quirks & Quarks

Cane toad tadpoles in Australia are cannibalizing smaller cane toad hatchlings

The invasive cane toad hatchlings have evolved an escape strategy to evade cannibalism, but it comes at a price.

The hatchlings have evolved an escape strategy to evade cannibalism, but it comes at a cost

Cane toads are causing a lot of problems in Australian ecosystems because the invasive species has no predator to keep their numbers in check and they're poisonous. (Ian Waldie/Getty Images)

Invasive cane toads have become so abundant in Australia that the tadpoles are getting rid of their competition by cannibalizing hatchlings, which in turn is driving evolution of new behaviours to avoid being eaten.

The tadpoles have such a ravenous appetite that as soon as a cane toad lays eggs in a pond, tadpoles already present in the water can sniff them out and will attack and consume them until often, there are no hatchlings left.

In the 1930s, cane toads were introduced to Australia in the hopes they'd help sugarcane farmers by gobbling up pesky beetles that were threatening their crops. 

Without any natural predators or diseases to keep the poisonous cane toads in check, their population has multiplied to epic proportions and is now wreaking havoc on Australian ecosystems.

There are now more than an estimated 100-million cane toads in Australia and they’ve turned out to be an ecological nightmare. (Ian Hitchcock/Getty Images)

Jayna DeVore studied this unusual cannibalistic behaviour as a post-doctoral candidate at the University of Sydney. She was curious about whether the behaviour was new, so she compared Australian tadpoles to those from cane toads collected from their native range in French Guyana.

DeVore told Quirks & Quarks host Bob McDonald, that they found the Australian cane toads had a much keener appetite for hatchlings than the non-invasive cane toads.

Tadpoles cannibalizing hatchlings in a pond in Australia. (Jayna DeVore/PNAS)

Her team also found that when hatchlings get a whiff of invasive tadpoles nearby, they have evolved the ability to speed up their development to reach the tadpole stage earlier so they are no longer vulnerable to cannibalization.

But that slight advantage came at a cost: when the hatchlings prematurely transform into tadpoles to escape being cannibalized by increasing their rate of development, they don't survive as well and grow and develop more slowly as tadpoles.

Produced and written by Sonya Buyting. Click on the link at the top of the page to hear the interview with Jayna DeVore.


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