Rotten but not forgotten
I’m walking over the red sandy dunes that dominate the landscape of Bush Heritage’s Ethabuka Reserve, a conservation property on the edge of the Simpson Desert in far western Queensland.
For mid-winter the temperatures are up there, well into the 30s, and something in the air smells… rotten.
I'm approaching one of the many 'carcass subsidy' sites that we're monitoring across the reserve. Using motion-sensor cameras and animal carcasses fastened to stakes (to prevent their removal). We're tracking the decomposition of animal remains, and the many scavenging creatures that visit to dine on this smelly meal.
Monitoring life and death
If you can get past the gross-factor, monitoring carcasses provides a great way to survey wildlife and observe a variety of species in their natural habitat. And, when working in sparse arid systems, carcasses can provide a strong attractant to draw in animals that are often spaced few and far between.
But at Ethabuka, we aren’t just using carcasses to survey wildlife. We're also monitoring death to understand how it impacts life.
For instance, along with nourishing hungry scavengers, carcasses also support plant growth through the nutrients they leech into the soil beneath. I witnessed this process after tracking the decay of a dead camel for over a year. A bit of rainfall was all it took to see greenery sprouting around the decaying animal.
Carcasses also influence some of the more vulnerable animals that inhabit Australian environments, by increasing the chance that they're eaten. This is because most scavenging animals are also very capable predators. So the mere presence of a carcass often creates a little hotspot of predator activity and a danger 'no-go' zone for anything that could be considered prey.
Using ‘fake’ bird nests positioned in areas with and without carcass subsidies, we showed that where carcasses were present, predation risk for ground nesting birds increased. Our experiment was part of a greater project investigating whether we could use carcasses to sustain dingo numbers in drought periods. The hope was that by supporting dingo populations, we could suppress predators such as the feral cat and red fox and thereby protect the countless small animals vulnerable to predation by these feral species.
However, not only did the carcasses increase the probability of nest attack, the meat they provided also filled the bellies of feral cats and red foxes. To add insult to injury, one fat tabby even managed to polish off an entire 40kg carcass in a matter of days! He obviously didn’t see the memo that feral cats aren’t generally considered voracious scavengers.
Still, many scavengers we recorded were native, such as the Little Crow and Australia Raven, as well as Wedge-tailed Eagles and Sand Goannas. Dingoes also made an appearance, but didn’t chow down on the carcasses as much as we thought they would.
Predators and parrots
While we couldn’t show that carcasses can be used to lessen the impact of feral predators, we're able to use this research to shed some light on other aspects important for the preservation of endangered species across Bush Heritage reserves.
For one, we've been able to use our findings to better understand some of the threats experienced by ground-nesting birds. This includes the endangered Night Parrot, which nests on Bush Heritage’s Pullen Pullen Reserve in western Queensland.
By designing some of our ‘fake’ nests to mimic Night Parrot nests, we identified Red Foxes as key nest-site predators and were also able to see some of the different strategies they used to access the eggs.
Night parrots typically build their nests in the very prickly, dense confines of spinifex grass, but we watched foxes either burrow under, or simply stick their heads straight into the barbed plants to grab their prize with ease.
Foxes are not present at Pullen Pullen but Bush Heritage is remaining vigilant by conducting regular feral predator controls and monitoring.
Our findings also suggest that land managers might need to be more cautious when controlling feral herbivores (e.g. Camels) in areas or at times when threatened native species are vulnerable to predation. A poorly positioned carcass could lead feral predators directly to the nests of some of the few Night Parrots in existence.
This project is supported by the Australian Government National Environmental Science Program's Threatened Species Recovery Hub and by Bush Heritage and all our generous supporters and donors.
Note: all animal carcasses used were collected as road kill or from pre-approved culls that occurred on adjacent cattle properties, so no animals were harmed for the purpose of this research.