SYDNEY, Australia — Australia’s northern quolls are small animals with big appetites — and they are eating themselves to death.
Nocturnal marsupials, about the size of a squirrel, quolls once roamed all of Northern Australia. But a disposition to eat just about any animal smaller than themselves led to a steady diet of cane toads, an invasive and poisonous species.
Since the 1900s quoll populations have plummeted. In parts of Cape York Peninsula in northeastern Australia, toad-eating quolls were completely wiped out, and the animal has been considered endangered nationwide since 2005.
But in one area of Queensland, scientists noticed that quolls did not have a taste for the deadly toad, and local populations were thriving. The secret to their success: a gene that made them averse to eating toads.
Beginning in 2016, ecologists at the University of Melbourne began breeding the Queensland quolls with others that lacked the toad-aversion gene. They soon discovered that all of the hybrid offspring inherited the survival gene.
Now scientists believe they can help restore diminishing populations across the country using a technique known as “targeted gene flow.” By selectively breeding quolls they can fast-track evolution, and introduce toad-averse quolls into areas where the amphibians have yet to invade. Experts hope that the same science of identifying favorable genes and introducing them naturally through breeding could help other endangered species, including the corals of the Great Barrier Reef.
“What we’re doing is nothing unnatural,” said Professor Ben Phillips, who conducted the research on the quolls and wrote a study published last month in Conservation Weekly. “It’s just matchmaking.”
Taking what they learned in the lab, Professor Phillips and his team released 54 mixed-gene quolls last year onto Indian Island, the eastern coast of Australia, which is home to a large toad population. In April, the scientists retrieved and tested the surviving quolls and found that offspring produced on the island all inherited the aversion gene.
The surviving quolls were later rereleased onto Indian Island to be left until next April, when scientists will discern whether the population has remained stable or, better yet, thrived. Quolls are prolific breeders, producing litters on average of five to eight babies once a year.
But cane toads are not the only threat quolls face.
Habitat loss, climate change and nonnative predators like foxes and feral cats have contributed to the quolls’ rapid decline.
“The problem for the quolls doesn’t have everything to do with pest management,” said Alberto Vale, the president of the Australian Quoll Conservancy. “We need to monitor the species, manage them and be conscious of them.”
The quoll experiment is promising, experts said, because it proves targeting genes to protect animals can be done safely and naturally.
“It provides an important message of hope that by using scientific tools we might be able to address some of these substantially important threats facing biodiversity, and that’s obviously particularly important in Australia, which has one of the worst conservation records in the world,” said Euan Ritchie, a senior lecturer in ecology at Deakin University in Melbourne.
