by Spot-tailed quoll numbers in north Queensland have dropped to critically endangered levels, new research on the threatened marsupials suggests.
For two years, scientists monitored populations of the North Queensland spotted-tailed quoll subspecies, Dasyurus maculatus gracilisIt lives in cold regions at high altitudes.
The population has halved previous estimates, from 500 quolls about 25 years ago, to 221 adult quolls, which meets the criteria for the subspecies to be listed as critically endangered under the Environmental Protection Act. and Conservation of Biodiversity.
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After the Tasmanian devil, the spotted-tailed quoll is the second largest carnivorous marsupial, with adult males growing to several kilograms and females weighing around 1.5kg. The species preys on animals such as opossums, bandicoots, rats, and birds.
Study co-author Conrad Hoskin, an associate professor at James Cook University, described the spotted-tailed quoll as a “faster, more agile version of a Tassie devil,” which is capable of climbing trees to catch its prey.
Using images captured with bait-activated camera traps, the researchers were able to identify individual quolls from the unique patterns of their spots.
Hoskin said there were six separate groups of northern spotted-tailed quolls that lived in different mountainous regions.
“The aggravating problem is that the total [number] it is divided into six small populations that range in size from around 10 individuals to around 100 individuals,” Hoskin said.
A key concern is that these isolated quoll groups are “in the realm of going into a downward spiral based on genetic problems,” he said. “If you only have 10 or 20 individuals, you can’t prevent related individuals from breeding with each other.”
Carnivores play a key ecological role, with Hoskin describing quolls as “the number one predator on mountaintops”.
Researchers are still not sure what is driving the population decline. Cane toad poisoning is one theory, but “cane toads have never been particularly common in the highlands of the humid tropics,” Hoskin said. However, she noted that “over the last decade or two, we’ve seen a lot of female toads make it…to the higher elevations.”
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“The other thing is that there is a lot of fragmentation and traffic in North Queensland, so there are definitely some hit-and-runs on the roads. Climate change could well be affecting them if it is affecting their prey, such as opossums and [other] small mammals.
“If you start to have inbreeding effects on top of other threats, it could really lead to pretty rapid declines.”
The northern subspecies of the spotted-tailed quoll is distinct from the northern quoll, a smaller quoll species that also occurs in Queensland and is also endangered.
The study was published in the journal Ecología Austral.
