Afterlife in the outback

This University of Sydney researcher is helping us understand how carcasses might be putting our native species at risk.

A cow’s body sprawled on a parched plain of red sand, stomach bloated and eyes missing, is an image of death that conjures the harshness of outback Australia.

But in the eyes of Emma Spencer, a PhD candidate at the University of Sydney, that carcass in the desert is an island of life in a sea of sand.

“Carcasses are incredibly interesting,” she says. Yet little research has been done on them. Emma has been studying the fate of carcasses on Bush Heritage’s Ethabuka Reserve, located on Wangkamadla country on the northern edge of the Simpson Desert in far western Queensland, for about two years now.

In the boom-and-bust of outback Australia, carcasses can be an important food source, even for species not usually thought of as scavengers like the Willie Wagtail.

While many carcasses arise from natural deaths, the control of feral animals, such as camels and goats, contributes many more.

“I’m really interested in exploring how [culling] – which occurs for the benefit of the system, whether for agriculture or conservation – could have unintended impacts,” she says.

For her research, Emma sourced animal remains from road kill or approved sources. She relocated the carcasses to the reserve, fixed each in place to stop scavengers from dragging them away, and set up remote wildlife cameras to see which animals came to feed.

The carcasses attracted all sorts of scavengers, from native Wedge-tailed Eagles, Sand Goannas and Dingoes to introduced Red Foxes and feral cats. But all these species are also predators, on the lookout for other easy meals nearby. This means that for some vulnerable animals the mere presence of a carcass could increase their chances of being eaten.

To understand whether the presence of dead animals affects ground-nesting birds, Emma made fake Little Button-quail (Turnix velox) and Night Parrot (Pezoporus occidentalis) nests and placed them in areas with and without carcasses.

Buttonquail nests are little more than a scrape in the sand furnished with a few feathers, and they're usually located at the edge of clumps of vegetation. Night Parrots, on the other hand, build their nests deep within mounds of spiky spinifex grass.

While the endangered and highly elusive Night Parrot is not found at Ethabuka, it has been recorded in similar environments and in Bush Heritage’s Pullen Pullen Reserve.

Emma found that the fake Little Button-quail nests were raided most often by Little Crows and Australian Ravens.

“They’re everywhere,” she says. “They fly around these arid environments so quickly. But they couldn’t get into the Night Parrot nests – they just couldn’t stick their heads in there.”

Yet there was one animal that could get its head deep into a clump of spinifex to raid the fake Night Parrot nests: the Red Fox.

“The fox was so efficient. Every single time I saw a fox on a carcass, pretty much the same night all the eggs in that area would be gone,” says Emma.

Luckily, foxes are not present at Pullen Pullen but Bush Heritage regularly undertakes predator control on the reserve and monitors for their presence.

Emma’s research has shown that even small carcasses can have a big impact on the areas immediately surrounding them.

In the arid environment of the Simpson Desert a large carcass such as that of a camel may last more than a year. Emma has observed that these bigger carcasses are so valued that animals will return again and again, spraying them with urine to mark them as their territory.

If a camel carcass is left under a stand of Gidgee trees, where birds often nest in large numbers after heavy rain, it will probably attract feral cats and foxes and increase the risk of predation for those birds, says Emma.

To reduce these types of negative impacts, she says land managers need to be cautious when culling feral herbivores such as camels at times when other species might be particularly vulnerable, or, if culling must happen, move the carcasses away from sites where vulnerable animals are known to breed.

Yet it’s important to remember that dead animals are a natural and essential part of an ecosystem.

“The primary scavenger of carcasses in the Simpson Desert is the Wedge-tailed Eagle. They often arrive first and feed the most,” says Emma. “There are still a lot of positive things that carcasses do and we can’t forget that in our management.”