Young 'teachers' help native wildlife avoid deadly cane toads
Scientists from Macquarie University have come up with an innovative way to stop cane toads killing native wildlife by training goannas to avoid eating the deadly amphibians.
A study published in Conservation Letters outlines a strategy developed by Macquarie University researchers to protect native species from the impacts of invasive cane toads.
Led by wildlife biologist Dr Georgia Ward-Fear, the study showed high survival rates in goannas in Western Australia trained to avoid poisonous cane toads.
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Teacher toads: Dr Georgia Ward-Fear with a yellow-spotted monitor in the Kimberley region of Western Australia, with Balanggarra Rangers. Photo: David Pearson
"Cane toads crossed into Western Australia in 2009 and have made it most of the way across the Kimberley, with disastrous results," says Dr Ward-Fear.
"When apex predators like goannas eat an adult cane toad, they die quickly and painfully – and when they disappear, it affects the whole food web."
Together with Macquarie University evolutionary biologist Professor Rick Shine, Dr Ward-Fear ran small-scale field trials in 2016 showing when lizards are first exposed to younger, smaller cane toads, they get sick from eating them, but don’t die. Most will then avoid eating another cane toad and survive.
"It's a form of ecological immunisation, building resilience in native wildlife against invasive species," Dr Ward-Fear says.
The study field-tested this 'conditioned taste aversion' method on yellow-spotted monitors heavily impacted by cane toad spread. At control sites without the small 'taster toads', goanna populations plummeted by up to 94 per cent. At taste aversion sites, populations ranged from 35 per cent to 140 per cent of pre-invasion levels.
“The strategy involved releasing thousands of eggs, tadpoles and juvenile cane toads into wild waterbodies in the Fitzroy Valley in Western Australia's Kimberley region, immediately ahead of the invasion frontline,” says Dr Ward-Fear.
This ambitious approach depended heavily on collaboration with the Cane Toad Coalition, a group of research, conservation and land management organisations coordinated by Dr Ward-Fear and Professor Shine, and supported by an Australian Research Council grant.
Working with the Bunuba Rangers and the Western Australian Department of Biodiversity, Conservation and Attractions to raise then release juvenile toads, the team used camera traps and sardine-tin baits to observe goanna populations.
"As cane toads arrive, we see a very rapid and huge decline in the larger predators which regulate the food web from the top. This imbalance sends ripples through the whole ecosystem," says Dr Ward-Fear.
Goannas are significant cultural totems for Traditional Owners and an important bush tucker food.
The intervention targeted specific populations, but its results will have long-term impacts.
"By managing the initial impact of the invasion, we see ongoing survival of goanna populations because after cane toads invade and begin breeding, plenty of baby toads will 'train' the next generation of goannas, without us having to keep adding more toads to the system."
The research shows behavioural interventions can be a viable alternative to traditional approaches that try to wipe out invasive species.
"While it's impossible to deploy 'teacher toads' right across the Australian tropics, we can maintain pockets with healthy predator populations, and potentially these can repopulate areas where goannas have become locally extinct," says Dr Ward-Fear.
"We're optimistic that even a single deployment can have long-term effects."
Citation: Ward-Fear, G., Rangers, B., Bruny, M., Everitt, C., & Shine, R. (2024). Teacher toads: Buffering apex predators from toxic invaders in a remote tropical landscape. Conservation Letters, e13012. https://doi.org/10.1111/conl.13012.
Mislabelled shark meat rampant in Australian markets
A study by Macquarie University researchers has revealed widespread mislabelling of shark meat in Australian markets, including the sale of threatened species.
The findings, published in Marine and Freshwater Research, highlight the ineffectiveness of seafood labelling and the implications for consumer choice and shark conservation.
Researchers collected 91 samples of shark meat from 28 retailers across six Australian states and territories. Using DNA barcoding, they identified the species of each sample and compared it with the retailer's label.
Around 70% of the samples were mislabelled, either because the species did not match the label or the label did not comply with the Australian Fish Names Standard (AFNS). Mislabelling was particularly high for samples labelled as 'flake', which the AFNS restricts to just two sustainably caught shark species. The research found that 88% of 'flake' samples were from neither of these species.
"Our research shows that mislabelling of shark meat is a widespread problem in Australia," said Teagan Parker Kielniacz, the study's lead author. "Consumers assume that because you can buy flake, it is a sustainable choice, but it's a bit more nuanced than that; most flake was not from sustainably caught shark species."
The study identified nine samples from three threatened species, including the critically endangered scalloped hammerhead and school shark, all sold as 'flake'. Mislabelling was markedly higher in takeaway shops compared with fish markets and wholesalers.
The research underscores the urgent need for improved labelling standards and enforcement. "Many shark populations are facing unprecedented declines worldwide, and yet consumers have little idea of the provenance of the fish they are eating, and they are not told they are eating a threatened species," says co-author Nicolette Armansin.
Professor Adam Stow, the study's corresponding author, says DNA testing is rapidly becoming cheap, flexible and fast enough to enable large-scale monitoring of the seafood supply chain. Rapid screening methods, such as testing bilge water from fishing boats or wastewater from fish markets, could be used to determine what species have been caught or traded.
"Everybody wants to trust that what they're eating is what the label says it is," Ms Parker Kielniacz says. "Our study found that for 70 per cent of samples, we're not getting what's on the label – that's really significant."
Professor Stow says this research shows giving consumers access to accurate information is vital for building a more ethical and sustainable shark meat industry in Australia.
Citation: Parker Kielniacz Teagan J., Stow Adam J., Armansin Nicolette C. (2024) High levels of mislabelling of shark flesh in Australian fish markets and seafood shops. Marine and Freshwater Research 75, MF23198. https://doi.org/10.1071/MF23198
Stargazing in broad daylight: How a multi-lens telescope is changing astronomy
In a paper published in Publications of the Astronomical Society of Australia today, astronomers at Macquarie University have successfully tested a new technique for observing celestial objects during the day using the Huntsman Telescope.
This unique array of 10 camera lenses, originally designed for ultra-sensitive night sky observations, can accurately measure stars, satellites, and other targets even when the Sun is high overhead.
The research team used special 'broad band' filters on a test version of the telescope to block most daylight while allowing specific wavelengths from celestial objects to pass.
“People have tried observing stars and satellites in optical wavelengths during the day for centuries, but it has been very difficult to do. But our tests show Huntsman can achieve remarkable results in daylight hours,” says lead author, astrophysics PhD candidate Sarah Caddy, who helped design and build the Huntsman Telescope.
Macquarie's Huntsman Telescope observing space during the day
The Huntsman's daytime capability allows continual monitoring of bright stars like the red supergiant Betelgeuse, which can be unbservable at night for months at a time when its position is close to the Sun.
Betelgeuse dimmed substantially from late 2019 through 2020, likely due to a major ejection of gas and dust.
“Without this daytime mode, we'd have no idea if one of the brightest stars in the sky has gone supernova until a few months after its explosive light reached Earth,” says co-author Associate Professor Lee Spitler, Head of Space Projects at Macquarie's Australian Astronomical Optics (AAO).
The study also has significance in the rapidly expanding field of space situational awareness (SSA), the close monitoring of the ever-growing population of satellites, space debris and other artificial objects orbiting Earth.
With plans launch a further 50,000 low Earth orbit satellites in the next decade, there’s a pressing need for dedicated day and night telescope networks to continually detect and track satellites and visually check their composition, age and condition.
“Opening up to daytime observation of satellites allows us to monitor not just where they are, but also their orientation, and adds to the information we get from radar and other monitoring methods, protecting against potential collisions,” Ms Caddy says.
“Being able to do accurate, round-the-clock observations shatters longstanding restrictions on when astronomers can scan the heavens,” says Associate Professor Spitler.
“Daytime astronomy will be increasingly critical as we enter the next Space Age.”
Citation: Caddy SE, Spitler LR, Ellis SC. An Optical Daytime Astronomy Pathfinder for the Huntsman Telescope. Publications of the Astronomical Society of Australia. Published online 2024:1-19. doi:10.1017/pasa.2024.43.
