Dingoes are cunning predators and no friend to Australian sheep farmers, but they could play a pivotal role in suppressing the number of feral cats that devastate the country鈥檚 wildlife.
You can find non-native feral cats in just about every part of Australia. They have contributed to the extinction of 20 native mammals and threatened many more. As such, they are seen as a pest by many people.
Dingoes are a pest too, in the eyes of many sheep farmers. They arrived in Australia between 5000 and 10,000 years ago and quickly spread. Their deadly impact on livestock was so severe that about a century ago, the authorities began construction on what is now a 5600-kilometre-long fence, stretching from near the east coast of Queensland to near the south coast of South Australia. The fence formed part of a strategy, together with culling, to remove dingoes from the fertile land of the southeast corner of the country.
Advertisement
But the fence has also given biologists a research opportunity. By studying ecosystems on both sides, they can assess how wildlife 鈥� particularly prey animals and feral cats 鈥� behave in the presence or absence of dingoes.
Between 2011 and 2017, Mike Letnic and his colleagues from the University of New South Wales, visited sites on both sides of the fence. They collected cat and dingo faeces, as well as information on sightings of both predators. They also gathered data on the abundance of rabbits and dusky hopping mice, which are among the most common prey for feral cats and dingoes.
Dingoes were around 65 times less common on the southeast side, whereas cats were 5 times more common. The prey species were almost 11 times less common on the southeast side of the fence.
As expected, cat populations rose and fell in line with the abundance of prey on the southeast side of the fence. This indicates that the availability of prey is driving their numbers, Letnic says.
On the opposite side, where dingoes were more common, the numbers of cats and dingoes initially mirrored the abundance of prey. But there was a decline in prey in 2013 鈥� and the numbers of cats never recovered, even as prey numbers increased again. In other words, it seems that dingoes might help keep cat numbers down in some situations.
The study shows how dingoes could be important in the protection of native wildlife longer term, says Chris Johnson at the University of Tasmania, who was not involved in the study. 鈥淐ats were not able to respond to increased prey availability in the presence of dingoes,鈥� he says.
Johnson says cat numbers typically increase in the years following rain, most probably because rain leads to a boom in rabbit numbers.
An analysis of the scat showed the predators had a similar diet, but Letnic says that food competition wasn鈥檛 the only thing keeping cat populations down. The cat remains in a small proportion of dingo faeces suggested that dingoes help keep cat numbers down by killing them too.
The debate isn鈥檛 over
However, Benjamin Allen, at the University of Southern Queensland, is sceptical of the conclusions.
鈥淚t鈥檚 an interesting correlative result that many people have speculated on before,鈥� he says. 鈥淏ut the long-term experiments we鈥檝e done at the same site and at the same time have shown it not to be true.鈥�
In an experiment that tracked the effects of dingo culling at nine sites across Australia, over many years, Allen and his colleagues found no changes to cat and fox populations, or to the health of wildlife populations.
鈥淚 find it difficult to put my faith in correlations when manipulative experiments have shown otherwise鈥�, he says.
Ecosystems
