Sleepy lizards perk up when they smell fire

The Australian sleepy lizard (Tiliqua rugosa) does what it says on the tin. Sleepy lizards live their lives in the slow lane: they move lethargically and are inactive for long stretches of time. However, their slow lifestyle poses a problem. Sleepy lizards often live in dry and arid areas in Australia that experience regular fires, which are a threat to a slow-moving lizard. This led Chris Jolly and a team of researchers at Macquarie University, Australia, to explore whether sleepy lizards could sense fire, and how they might do so.The researchers already had an inkling that the lizards had some fire detection ability, thanks to zookeepers on the other side of the world accidentally burning their lunch. Staff members at Audubon Zoo, USA, noticed that their captive sleepy lizards started flicking out their tongues seemingly in response to the overcooked lunches. In addition, the reptiles began to move around their enclosures as though trying to escape. Lizards use their tongues to detect odours in the air – effectively they use their tongues to smell – so perhaps they were responding to the smell of burning food. To test whether and how lizards might sense fire, the researchers caught ten sleepy lizards from the wild and presented them with two indications of approaching fire: the smell of smoke, and the sound of a wildfire.When the researchers burned dried grass near to the lizards – but out of sight, so they could only smell the smoke – the lizards became much more active, moving more as though trying to flee the source of the smoke. By contrast, when the researchers played recordings of the sound of a wildfire alone, the lizards did not seem to try to escape the sound, moving around even less than when they were just played white noise.The researchers concluded that the lizards could smell fire and became more active in order to try to escape the impending danger. However, their lack of response to the sound of fire suggests that they don't use the crackling of burning vegetation to sense an oncoming inferno. This might be because smell is better for sensing fire in the lizards’ open habitats: smoke travels far and fast, providing an early and reliable warning of fire. Sleepy lizards might also be more sensitive to smells than to sounds – even though other animals, including even some other species of lizard – do react to the sound of fire.Perhaps surprisingly, even though sleepy lizards clearly responded to smoke, they did not flick their tongues more when smoke was in the air. This could be because they were so attuned to the smell of smoke that they did not need to flick their tongues more than normal in order to sense it and start moving.Because wildfires occur infrequently, with tens or hundreds of years between them, the individual wild lizards that the scientists studied may never have experienced fire during their lifetime. This probably means that their response to smoke is instinctive, rather than learned through previous experience of fire, which makes sense. Instinctive responses to smoke mean that even a lizard that has never experienced fire knows when to flee.So, sleepy lizards are keenly attuned to the warning smell of smoke and if you ever want to perk one up, all you need is some smoke.