Few creatures can outrun a forest fire as it engulfs everything in its path. For small marsupials, such as fat-tailed dunnarts and yellow-footed antechinus, the best hope is to nestle deep down in burrows and in nests in rocky fissures until the inferno has passed over. However, the aftermath can be equally as risky as the flames themselves. ‘We were interested in how animals can survive after a fire, when the landscape is often devoid of food and vegetative ground cover’, says Clare Stawski, from the University of New England, Australia. Having already discovered that one successful survival strategy is to hunker down and go into torpor – when the animal lowers its body temperature and reduces its metabolic rate to conserve energy – Stawski and her colleagues Fritz Geiser, Julia Nowack and Gerhard Körtner were curious to find out which factors trigger the onset of torpor in animals that have survived a blaze.
Reasoning that the food scarcity is a cue that could trigger an energy-conserving drop in body temperature, Stawski and her colleagues also wondered whether smoke and the environmental scars that remain – such as ash and charcoal – could also trigger torpor in antechinus wildfire survivors. ‘It took several weeks to capture enough animals in the wild’, says Stawski, who explains that the nocturnal animals are most active on warm nights; ‘our capture rates were often sporadic and influenced by the weather’, she recalls. Back in the lab, Stawski and Körtner gently inserted minute temperature loggers inside the animals’ body cavities before allowing them to roam free in an enclosure. Then, Stawski and Nowack embarked on a month-long series of experiments in which the antechinus experienced a series of situations that they might undergo during and after a fire, including: smoke billowing through the enclosure, reduced food supply and, on one occasion, ash and charcoal spread over the ground to simulate the conditions after a firestorm. Meanwhile, the team recorded the marsupials’ body temperatures in search of the tell-tale temperature dip that is the hallmark of torpor.
Remarkably, each of the scenarios triggered a significant drop in the animals’ body temperatures. While the females doubled the amount of time that they dropped their body temperatures to conserve energy in response to each of the wildfire scenarios, the males increased the amount of time when they were torpid 6.5-fold when smoke filled the enclosure and their food supply was reduced by half. However, when Stawski and Nowack spread ash and charcoal throughout the enclosure, the small marsupials increased the amount of time they were torpid by 14.3-fold. ‘We were surprised that the combination of charcoal and ash with smoke and food reduction elicited such a strong response’, says Stawski. In addition, she noticed that the usually nocturnal animals became significantly more active during daylight at the first sniff of smoke. She says, ‘It is likely that smoke is perceived as a warning signal’, which probably gives the animals a chance to find a refuge and improve their chances of survival.
Having discovered that antechinus use a combination of cues – including charred remains, ash, smoke and food reduction – to trigger torpor and hunker down in the wake of an inferno, Stawski is now keen to learn more about how antechinus populations recover after fire has swept through.
