Lizards smell wildfire smoke and run before flames arrive

Wildfires are not just walls of flame, they are also clouds of chemical signals in the form of smoke. Australian sleepy lizards can read one of those signals and move before the heat arrives.

A new study shows these stout, blue-tongued reptiles recognize smoke as trouble and try to get away, yet they stay put when they only hear the sound of fire. The work was led by Dr. Chris Jolly of Macquarie University.

How lizards sense smoke

Sleepy lizards (Tiliqua rugosa) are large skinks from a group of smooth-scaled lizards that are common across Australia. They live in open country where fire is part of the landscape.

The team asked whether these lizards respond to smoke, a chemosensory cue detected by the tongue and a specialized organ in the roof of the mouth. They also tested the auditory cue of recorded fire sounds to see if noise alone spurs escape.

Scientists exposed wild-caught adults to brief puffs of smoke and to an odorless water vapor control, then played crackling fire versus white noise in separate trials.

They tracked movement with overhead cameras and counted tongue flicks, which is a basic olfactory sampling behavior.

Each lizard experienced all four treatments on three separate days, giving a robust set of repeated measures to compare responses.

All trials followed a one hour acclimation and ten minute pre-trial recording to capture baseline behavior.

Lizards react to smoke

The lizards fled from smoke but not from sound, and the numbers were clear. After smoke, they moved about 69 percent of the time versus 38 percent after water vapor exposure.

In addition, they traveled roughly 70.7 feet (21 meters) compared with 22.7 feet (6.9 meters) in the control.

They did not increase tongue flicking when smoke wafted in, which hints that a single sample was enough to detect the cue.

In the sound tests, movement increased with white noise exposure but did not translate into longer escapes, so the noise seemed more like a startle than a signal.

Results like these point to a sensory priority that fits a reptile built to read scent. Smoke spreads far ahead of flames, so it can serve as an early warning in open habitats.

“Our findings provide empirical support for the hypothesis that chemosensory cues of fire elicit escape responses in animals from fire-prone regions,” wrote Dr. Jolly.

That conclusion matches what zookeepers once noticed anecdotally when captive lizards reacted to a lunch that got burned and smoky.

Smell is stronger warning

For many lizards, smell carries more reliable information than sound about threats. Hearing is useful, but their ears are not tuned like a bird’s or a mammal’s for fine detail.

Chemicals in smoke bind to receptors and tell an animal that combustion is happening nearby. That signal is hard to fake and less likely to be background noise from wind or insects.

The study’s authors note that response to sound can vary by species and setting. In these trials, smell carried the day for escape decisions.

How other animals read fire cues

Some mammals wake from torpor, a low-energy rest state, when they detect smoke according to a prior study. For example, torpid eastern pygmy-possums are able to sense smoke and can climb in response.

Bats in deep torpor also respond to smoke, raising breathing and heart rates before they attempt to fly. That work warns that colder conditions can slow their reaction time.

Reptiles show patterns too, with a Mediterranean lizard reacting more strongly to smoke in populations from fire-prone places.

In California, western fence lizards change their behavior when they hear recorded fire sounds, and the effect depends on local fire history.

Why this matters for conservation

Fire conditions are changing fast, and extreme wildfires are becoming more common in many regions, a global analysis reports. That trend means animals will face more frequent and intense smoke cues across big landscapes.

Species that key in on smell may be able to leave sooner, but only if they have a path to safety. Fragmented habitats, roads, and fences turn timely decisions into dead ends.

Managers can use these findings to plan burns and to design refuges with early escape in mind. Simple steps like open corridors, shelter patches, and fewer barriers around core habitat can make a difference.

When possible, crews can avoid colder days that slow arousal in resting mammals, and keep the timing and location of routine burns aligned with animal movement seasons.

Coordination across property lines helps maintain escape routes that actually lead somewhere safe.

What it means for people

The results underscore a point that is easy to miss when we only count animals after a blaze. Survival often depends on seconds, and the right cue at the right time could prompt the move that saves a life.

When agencies schedule prescribed burns, cooler days can reduce risk to species that react more slowly to smoke, as prior work on torpor suggests.

Urban planners can protect wildlife by keeping escape routes intact near high-risk zones.

The study is published in Biology Letters.

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