Goanna lizards could save Australian farms millions

Scientists at the University of Cambridge have found that giant lizards called heath goannas could save Australian sheep farmers a lot of money each year by keeping blowfly numbers down. The goannas act as natural clean-up crews by clearing maggot-ridden animal carcasses from the landscape. To explain more is Tom Jameson from the University of Cambridge’s Department of Zoology…

Tom - So rewilding projects are this form of landscape restoration where we're looking to reintroduce locally extinct species in order to restore the functions and services they provide to ecosystems. And what I've been really interested in studying is the role that reptiles might play in these sorts of projects, as they've been massively overlooked. So we wanted to study the role of reptiles when it comes to rewilding projects.

Chris - Which reptiles? I can imagine, given the geography you've referenced, South Australia, I can imagine what you're going to say, but what sort of reptiles specifically?

Tom - So I've been working on looking at monitor lizards as a bit of a case study for this project. So these are monitor lizards or goannas. This is the group that includes the Komodo dragon and its relatives. And they have a really high diversity in Australia of the 80 species worldwide. There's around 30 or so in Australia. And so we've really focused in to see how they could be managed and included in rewilding projects.

Chris - Some of them are really big. You say Komodo Dragons? Some of the ones I've come across in Australia are massive.

Tom - Absolutely. Yeah. So we've got species like the perentie that live right in the centre. And these are beautiful. They're the second largest lizard in the world after the Komodo dragon. They can get over two metres long. And I've been looking at another relative of the Komodo dragon, the heath goanna. So these are a lovely, very pretty species. They sort of range from a glossy black to an olive brown covered in these, these beautiful yellow spots and stripes. And they live down on the south coast and they grow to about 1.5 metres long.

Chris - Have you gone about it?

Tom - We worked down with the Marna Banggara project. So this is a Rewilding project down on the south coast of Australia, right in the centre of the south coast of Australia on a place called the Yorke Peninsula. This project aims to restore 170,000 hectares of landscape. So this is roughly the footprint of the size of London. So it's a really, really massive area. And from this area most of the native mammals have been lost. Most of the native species have been lost. So 90% of the native mammal fauna is gone from this huge region, mainly as a result of predation by invasive foxes and cats. And so the wider project, what they seek to do is to reintroduce these native species in order to try and restore that landscape. So the project was very focused on mammals and what we wanted to focus on was what the role of reptiles might be in this project, particularly these heath goanna, as I've mentioned, these 1.5 metre long lizards, how they might be able to contribute to restoring this landscape to these ecosystem services.

Chris - Do you mean as in, in terms of, as you restore the landscape, their numbers change and the landscape responds to their numbers changing, so it's like a domino effect. Is that what you mean by what they do? Or is it that they're already there and as the landscape rewilds, they make a contribution to that process or both?

Tom - A little bit of both. The idea is that what we want to study is if we're looking to boost their numbers, so by either reintroducing individuals to help grow the population or by doing specific conservation measures to help those populations grow the knock-on effects that they will then have as their populations grow by the different things they do in the landscape. And so in this case, we wanted to look at specifically how as those populations grow through conservation measures, how they're contributing to scavenging and what benefits that might have for the wider ecosystem

Chris - And what do they contribute?

Tom - So what we found is that they are really, really effective scavengers. They remove large amounts of carcasses from the landscape and that reduces a lot of the problematic things that might breed in these carcasses. So things like blow flies, animals that cause disease, we find the presence of these heath goannas removes this from the landscapes. They're providing a really, really important service.

Chris - And presumably, I mean, there’s enormous number of flies around us here, probably preying on us here in Grantchester. But presumably if you remove those flies, because one of the other big Australian industries is going to be things like sheep and cattle. Does that have a knock on benefit for those industries?

Tom - Absolutely. Yeah. So I mean, one of the reasons we were interested in looking at the effects that these heath goannas might have on blowfly populations is because in this wider landscape we're working in, there's a lot of sheep farms. And a big problem for these sheep farms is these blowflies. They cause a disease called fly strike, a really horrible disease. The blowflies will lay their eggs on the wool of sheep. Those eggs hatch into maggots and they borrow into the sheep's flesh, start to eat them alive. It's a very costly disease as well. This costs the Australian sheep farming industry $280 million a year. And so any role of a native species that might be to reduce these numbers of blowflies, reduce the incident incidences of this disease could have really positive effects, quite big financial effects. And so that's what we find, we find these goannas, they reduce the numbers of these blowflies and that potentially reduces incidences of this disease that might have some big positive effects for the agricultural industry too.