Sometimes, science begins with the simplest of observations—or even an accident. Years ago, zookeepers in the United States noticed something curious. As they burned their lunch, the acrid smoke drifted through the building. To their surprise, the sleepy lizards housed there suddenly became restless. These squat, blue-tongued reptiles tongue-flicked, paced, and tried to escape their enclosures. Other reptiles nearby remained calm, but the sleepy lizards seemed deeply unsettled.
At the time, it was just an amusing story—a quirk of the animals. But now, researchers in Australia have tested the phenomenon under controlled conditions. Their findings, published in Biology Letters, reveal something remarkable: sleepy lizards (Tiliqua rugosus) can innately recognize the smell of smoke as a signal of danger and attempt to flee. They do not, however, react to the sound of fire.
Nature’s Alarm System
Sleepy lizards, also known as shinglebacks, are common across Australia’s semi-arid landscapes. These habitats are shaped by fire, and over millennia, species have had to adapt to its destructive force. Unlike humans, who rely on sight and hearing to notice approaching flames, these lizards appear to use smell as their primary early-warning system.
When researchers exposed captive sleepy lizards to smoke, the animals became agitated. They flicked their tongues, tested the air, and tried to escape. When exposed to the crackling sounds of fire without smoke, they remained calm. The difference is clear: sound alone doesn’t trigger survival behavior, but the chemical signature of smoke does.
“Many animals from fire-prone regions, such as Australia, appear to have this miraculous ability to survive their homes being burned,” explained lead author Dr. Chris Jolly of Macquarie University. “Our study demonstrates that some lizards innately recognize smoke as a cue of approaching fire and respond by running away.”
Evolution in a Fire-Prone World
Australia is a continent built by fire. From eucalyptus forests that rely on flames to release seeds, to grasslands that burn and regenerate in cycles, fire is not just a threat—it is part of the ecological rhythm. For animals, this means survival often depends on detecting fire before it arrives.
The new study suggests that sleepy lizards have evolved sensory systems shaped by this fiery environment. Their keen response to smoke may be hardwired, not learned, since even captive-bred individuals showed the same behaviors. This innate ability could be the difference between life and death when wildfires sweep across their habitats.
But evolution is not a guarantee of safety. Climate change is rewriting the rules. Fires are becoming hotter, faster, and more widespread—even in ecosystems like rainforests that historically burned rarely. For species adapted to slower-moving or less intense fires, the new conditions may overwhelm their survival strategies.
Fire, Animals, and the Climate Crisis
As the planet warms, wildfires are intensifying worldwide. Australia’s Black Summer of 2019–2020 burned over 24 million hectares, killed or displaced an estimated three billion animals, and shocked the world with its scale. Similar stories are unfolding across California, the Amazon, and the Mediterranean.
Against this backdrop, studies like the one on sleepy lizards are more than scientific curiosities—they are urgent. Understanding which species can detect fire cues, and which cannot, will help conservationists predict vulnerabilities. Animals that can smell or sense fire may find ways to survive; those without such instincts may be at far greater risk.
Survival Strategies Beyond Lizards
Sleepy lizards are not alone in their fire awareness. Birds of prey in northern Australia, such as black kites, have been observed intentionally spreading fires by carrying burning sticks to flush out prey. Some mammals burrow deep into the soil as flames pass overhead. Insects may fly toward safe zones when smoke thickens.
Each strategy is a thread in a larger tapestry of survival, woven by countless generations exposed to recurring fire. But the rapid changes we are witnessing now—more frequent fires, longer fire seasons, and blazes in historically fire-free ecosystems—pose new challenges. Evolution is slow; climate change is fast.
Lessons from the Smoke
The discovery about sleepy lizards is both fascinating and sobering. On one hand, it highlights nature’s resilience: animals are not passive victims but active participants in survival, armed with ancient senses honed by fire. On the other, it reminds us that adaptation has limits.
As Dr. Jolly notes, “As fires become more frequent, intense and unpredictable—including in habitats that rarely burned in the past, like rainforests—we need to know which species can respond to fire cues, and which are most vulnerable.”
The smoky signal that drives sleepy lizards to flee is a small piece of a much larger puzzle. It teaches us that if we want to protect wildlife in an era of escalating fire, we must listen carefully to how species respond, and act to preserve the habitats that allow those instincts to work.
A Story of Fragility and Strength
In the end, the tale of the sleepy lizard is not just about one species. It is about how life itself bends and adapts to the harshest of forces. It is about fragility—animals threatened by flames far larger than themselves. And it is about strength—the ability to detect danger and run, a survival dance choreographed over millennia.
As fires burn hotter and longer, we are reminded that survival is not guaranteed. But in the flick of a lizard’s tongue, in its restless pacing at the first whiff of smoke, we glimpse the profound intelligence of evolution—and the urgency of protecting it in a world where fire no longer behaves as it once did.
More information: From anecdote to evidence: experimental validation of fire-cue recognition in Australian sleepy lizards, Biology Letters (2025). DOI: 10.1098/rsbl.2025.0364
