Dr Jonathon Howard, NPA Executive
Every ecosystem has certain species that are critical to the survival of the other species. They are sometime labelled ‘keystone species’. New research is showing wombats may play an increasingly important role in the survival of other species as our environment becomes more fire prone.
Although New South Wales is home to a spectacular variety of plants, animals, and ecosystems, our biodiversity faces a number of pressures, including those that arise from climate change.
How fauna responds to fire is particularly important as fire is a widespread process across the globe. In fact, fire burns 3-5% of the planet every year. Australia has recently experienced what scientists are labelling ‘mega-fires’ – a new phenomenon brought about by climate change. It has been estimated that three billion animals – mammals, reptiles, birds, and frogs – were killed or displaced by Australia’s devastating 2019-20 megafire.
What do native animals do to cope with fire?
Our story begins back in 2018, when the Audubon Zoo in the United States had a number of stumpy tail/ shingle back lizards (Tiliqua rugosa) for their ‘Reptile Encounter’ experience. Some of these were on public display while others were in an off-exhibit backup area in the staff tea room. Funnily enough, the ones in the off-exhibit area were inadvertently exposed to light smoke due a staff member accidentally burning a pastry in a toaster in that room. The lizards that were exposed to the smoke began pacing swiftly, repeatedly tried to escape their enclosures, and began rapid olfactory-related tongue-flicking. Those that were on display, however, did not exhibit any change in activity or behaviour. Since there were no visible flames, sounds of fire, no reductions in light levels or visibility, or increases in temperature, the zookeepers suggested that the lizards were detecting smoke through smell. Not only that, because many of the lizards that reacted were captive bred, this response likely represents an adaptive innate behavioural response.
We now know that our wildlife uses a range of cues to sense fire in order to give them an ‘early warning’. They use a variety of senses: smell, sound, and slight. Some can smell fire, others detect the chemical compounds in smoke, or listen to the crackling sound of a fire. For example, more recently it’s been found that Gould’s Long-eared Bat and the Fat-tailed Dunnart are able to go into torpor (a type of mini-hibernation) during certain times of the year, but will wake up and try to escape if they are exposed to smoke. Estivating juvenile Reed Frogs (Hyperolius nitidulus) respond to playbacks of the sound of fire by fleeing in the direction of protective cover, where they are safe.
Because fire occurs periodically in a variety of habitats around the world, we now know animals that live in fire-prone habitats are ‘hardwired’ in a variety of ways to detect a fire.
How does wildlife survive a fire?
When you think about it, fire can not only kill wildlife, but it can also alter their habitat, and reduce or increase the availability of food, shelter, and other resources. Animals that live in these habitats are also ‘hardwired’ to also respond with behaviours which minimise the chances of getting killed. There is a variety of responses they use: they might flee the fire front, find a weak spot in the fire and ‘double back’, find temporary refuge and then leave the area weeks after the fire, or find a longer-term refuge and remain in torpor.
A study done on the megafires found expert ‘estimates’ for fire-related mortality were lower for species that could potentially flee or shelter from fire, and post-fire mortality estimates were linked to diet, diet specialisation, home range size, and susceptibility to introduced herbivores that damage or compete for resources.
So how do wombats fit in?
The role of species that burrow is increasingly recognised by ecologists concerned about the impact of fires. For example, burrows created by wombats could also serve as ecological refuges for a diverse array of other organisms. A recent study explored the ecological role of Common Wombat (Vombatus ursinus) burrows in a forest affected by the 2019–20 Black Summer fire. Using camera traps they found the activity of several species including Bush Rat (Rattus fuscipes), Agile Antechinus (Antechinus agilis), Lace Monitor (Varanus varius), Painted Button-quail (Turnix varius), and Grey Shrike-thrush (Colluricincla harmonica) increased at sites where Common Wombat burrows were present. The study found 56 different species of wildlife used wombat burrows (19 mammal species, 33 bird and four reptile).
The species that were more active at burrows tended to be smaller mammal and bird species that are vulnerable to predation, whereas species that avoided burrows tended to be larger mammals that might compete with Common Wombat for resources.
The burrows that wombats make are deep and complex. They can be over 15 metres long with multiple entrances and chambers. Wombat burrows seem to act as “fire refuges” – providing vital shelter, food, and even drinking water during and after a bushfire. They provide a valuable ecosystem function that might help other wildlife and suggests if we protect wombats in our forests it will benefit various species across many Australian fire prone ecosystems.