Australia — Some species of frogs can happily cope with the heat of bushfires by retreating to the safety of wetlands or the moist underground, new Australian research has shown.
Dr Katrin Lowe, from Griffith University, and colleagues, monitored four threatened wallum sedge frog species over two years as part of her PhD research.
Such frogs are dubbed ‘acid frogs’ because they are restricted to acidic coastal wetlands of eastern Australia, called the ‘wallum’ heathlands, which experience regular bushfires.
“Most research into the effects of wildfires on amphibians has been done overseas and we don’t know a lot about how Australian frogs respond to fire,” says Lowe.
The research, which has been published in the International Journal of Wildland Fire was undertaken at four national parks between the mid north coast of NSW to Cooloola in Queensland.
“Fire tolerant vegetation such as Banksia, Melaleuca, Leptospermum and grass trees characterise this area, which is regularly burnt,” says Lowe. “Acid frogs are known to have lived here for millions of years so it was clear they had some kind of survival strategy.”
The researchers monitored temperatures on land and in the water and found that fires altered the thermal properties of habitats by increasing ground temperature and widening daily temperature ranges.
Equipment that was not destroyed in the blaze showed that air temperatures reached as high as 57.6°C during the fire.
However, below ground and underwater, temperatures remained a reasonable 17.5°C, even during fires that burned the vegetation (and monitoring equipment) to a crisp.
“At the first sign of fire, frogs head for the safety of their wetland or moist underground,” Lowe says, adding that this strategy ensures the majority survive.
“About a week after the fire we found them perching on the stumps of burned out reeds, while other researchers have also reported the frogs calling only a few hours after a fire.”
Even if the population suffers losses, it rapidly recovers with breeding occurring as soon as there is enough water available to sustain tadpoles through to metamorphosis.
“Our observations suggest that acid frogs are highly adaptable and resilient and are able to breed in radically fire-altered environments,” says Lowe.
“However, their resilience depends on the conditions at the time: when it is wetter the frogs have more opportunity to hide, but during dryer and hotter periods there is a much greater chance of mortality.”
Studying how species respond to fire is really important for informing park fire management, says Lowe, adding that as a result of the research she was able to give management recommendations for burn regimes around for coastal wallum heathland.
“The best time to conduct hazard reduction burns is during cooler, wetter periods as these provide the best chance of survival and rapid population recovery,” she says.
“These findings also underscore the importance of long-term monitoring across the landscape when it comes to determining how species cope with fire,” adds Griffith University’s Jean-Marc Hero, who supervised the research.
“These frogs have more opportunities to escape than say a koala which might be stuck in a burning tree,” says Hero.
“However, the frequency of catastrophic fire events and the impacts they have on the surrounding vegetation and other wildlife will affect a population’s chances of survival.”
Under a dryer and hotter climate Hero says that we can expect more fires that could put populations at risk.
“We need to keep monitoring to understand what’s happening.”
This little frog thrives in acid environments and can be quite resilient to bushfires. (Source: Katrin Lowe)