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Alien cannibals could make Cape frogs croak, warn scientists

27 December 2018 - 09:42 By Dave Chambers
The Cape platanna is under threat from African clawed frogs, say scientists.
The Cape platanna is under threat from African clawed frogs, say scientists.
Image: John Measey

Cannibalism is rife in Cape Town ponds, say worried scientists.

They say the alien African clawed frog, which is known to eat its own tadpoles, prefers the taste of the indigenous and endangered Cape platanna.

The platanna lives in ponds throughout Cape Town, where the clawed frogs were introduced as pets and have taken over as an invasive species.

The African clawed frog in a tank.
The African clawed frog in a tank.
Image: 123rf.com/Brandy McKnight

Scientists at Stellenbosch University put clawed frogs in a tank with tadpoles of both species and found they preferred to eat the platanna offspring.

John Measey from Stellenbosch University
John Measey from Stellenbosch University
Image: sergsa.org

John Measey, a senior researcher at the Centre of Excellence for Invasion Biology at Stellenbosch, said his findings - published in the African Journal of Ecology - were “very bad news” for the platanna.

It may be necessary to forcibly remove African clawed frogs from these areas to protect the vulnerable native species, he said.

Co-author James Vonesh, an associate professor from Virginia Commonwealth University in the US who worked on the study during a Fulbright fellowship at Stellenbosch, told New Scientist: “It’s another interesting example where human alteration of the landscape has changed the playing field.”

African clawed frogs are found on four continents and have spread around the world, due in part to a significant pet trade in the 1950s and 1960s. They are native to cooler regions of sub-Saharan Africa, but not to Cape Town.

The frog’s name comes from the three short claws on each hind foot, which it uses to tear apart its food.