Birds of a feather
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How a fox stomach containing 63 centipedes could hold the key to understanding the effectiveness of feral predator management.
I'm a vegetarian, so it's a big step to be cutting into a cat or a fox stomach. It's definitely not for the fainthearted,” says Sara Petrovic, Monash University graduate, Bush Heritage intern and inaugural PR manager for centipedes.
Sara has just returned from Bon Bon Station Reserve, on Antakirinja Matu-Yankunytjatjara country in South Australia, where she's been undertaking a pilot research project on the relationship between invertebrates such as centipedes, spiders and scorpions, and feral cats and foxes.
Her mission: to discover whether invertebrate monitoring could help determine the effectiveness of Bon Bon’s feral predator control program.
At 216,500 hectares, Bon Bon’s buckshot plains, sand dunes and salt lakes are home to scores of native birds, mammals, reptiles and invertebrates.
In 2015, Bush Heritage commenced a large-scale feral cat and fox control program on Bon Bon to help protect those native species from predation. But in order to know if it’s working, we need to gather as much data as possible. That’s where dissections come in.
Bon Bon Field Officer Kate Taylor is no stranger to this grisly practice. Having overseen Bon Bon’s feral predator control program since its inception, Kate knows that dissecting cat and fox stomachs can give us a valuable insight into their diets and behaviours.
“We’ve found all sorts of small mammals, reptiles, invertebrates, and even weird things like centipedes and scorpions, which is surprising given centipedes have quite toxic venom – you would think the foxes would be getting stung,” says Kate.
“If you don't look at stomach content when you catch a fox or cat, you can’t get that information back. This practice has helped us build a good database, and taught us a lot,” she says.
Through 136 fox dissections and 59 cat dissections, Kate has discovered that invertebrates are a significant food source for predators on Bon Bon, with one fox stomach containing 63 centipedes alone. It was this realisation that led Kate to enlist Sara to begin her research project.
“Kate had the idea to survey invertebrates and see whether we can develop them into an indicator species that can tell us how well the predator management is working,” says Sara.
“Bon Bon has different management zones. Some have been subject to really intense predator management and others have been left as controls, so we can look at invertebrate numbers in the same habitat type across different zones and see how different levels of predator control affect them.”
To date there has been little research into the impact that feral predators have on invertebrate populations; invertebrates are generally understudied and often excluded from biodiversity surveys, despite the significant services they provide, such as pollinating plants and crops, dispersing seeds and cycling nutrients.
As well as comparing invertebrate populations in Bon Bon’s different management zones, Sara also trialled various methods for monitoring and capturing them: pitfall traps, hay bait-traps, active searches and dissections.
Among other things she found substantial differences in the abundance and biomass of invertebrates captured using two styles of pitfall traps.
The next step is to collect more data. Come Spring (pending COVID-19 restrictions), Sara and Kate will do another round of surveys to deepen their understanding of the interplay between feral predators and invertebrates.
Invariably, that will mean more dissections for Sara, but she knows it’s all for a good cause.
“It's a little bit disconcerting when you open up [a stomach] and you can just see bits and pieces of animals, like a foot, or tail, or a bit of fur. It’s challenging, but I think it's worth it for what you get out of it,” says Sara.
“We have lost so many of our plants and animals in this corner of Australia and I love to sit on this breakaway in the centre of the reserve and look out and pretend that they’re all still there."Read More