13/10/2026
🦎👅 Every tongue flick is a little investigation…
Watch a monitor lizard exploring and you’ll notice its long, deeply forked tongue repeatedly appearing. That movement helps the animal gather chemical information about the world around it — including clues that our eyes would miss completely!
This is called chemoreception, and monitor lizards are highly specialised for it.
🔬 How does “smelling with the tongue” actually work?
The tongue acts as a collecting tool. As it flicks out, it samples chemical substances from its surroundings, including the air and surfaces it touches.
When it retracts, the collected chemicals are transferred within the mouth to a sensory system called the vomeronasal system. Its paired sensory organs, also known as Jacobson’s organs, connect to the mouth through openings in the roof.
Specialised receptor cells detect the chemical information and send signals to the brain. The tongue collects the sample; the sensory organs help analyse it!
So, although we often say a monitor is “tasting the air”, this is a specialised chemical sense rather than tasting a meal in the way we do. (pubmed.ncbi.nlm.nih.gov)
👅 Why is the tongue forked?
Those two tips allow the animal to sample two slightly different positions at once.
Comparing chemical information from the left and right can help a fork-tongued reptile work out where a trail lies and which way to investigate. Think of it as gathering scent information in “stereo”!
This explanation is supported particularly well by research on snakes, which share this specialised tongue-and-vomeronasal arrangement with monitors. The fork provides spatial information as well as collecting chemicals. (pubmed.ncbi.nlm.nih.gov, pubmed.ncbi.nlm.nih.gov)
🍽️ How does this help a monitor find food?
An animal can leave chemical traces even when it is hidden from view. For an active hunter, detecting those traces gives another way to investigate its surroundings.
Monitor lizards can distinguish food-related chemical cues from other smells. In experiments, savannah monitors produced more tongue flicks in response to mouse scent than to control substances — evidence that they were responding to information associated with prey.
Repeated flicks allow a searching monitor to collect fresh samples as it moves. Its eyes and chemical senses work together, helping it locate and assess potential food. (onlinelibrary.wiley.com)
🌿 It is about more than dinner
Chemical sampling also plays a wider role in reptile behaviour. Depending on the species and circumstances, chemical cues can provide information about other animals, potential predators and possible mates.
A tongue flick is therefore part of an animal’s information gathering. By itself, it does not tell us exactly what the lizard has detected or what it will do next. (pubmed.ncbi.nlm.nih.gov)
🌊 What about mangrove monitors underwater?
Mangrove monitors are semiaquatic, spending their lives around both land and water. That makes the underwater side of their sensory world especially interesting! (pubmed.ncbi.nlm.nih.gov)
Water can carry chemical information too. Substances released by animals may dissolve, disperse or remain associated with submerged surfaces. A submerged tongue flick brings the tongue into contact with that watery environment.
The likely role of underwater tongue flicking in a mangrove monitor is therefore to collect chemical information for the same vomeronasal system it uses on land. However, the precise effectiveness of this behaviour in mangrove monitors is less well established than terrestrial scent sampling, so we should describe it as a likely function rather than a fully demonstrated underwater tracking system.
Research on northern water snakes shows why this distinction matters: tongue movements change between land, water and the water’s surface. Water affects both the tongue’s movement and the collection of chemical cues, so underwater sampling cannot simply be assumed to work exactly like sampling the air. (academic.oup.com)
🧠 A world of information we cannot see
For a monitor lizard, exploring involves much more than looking around. Each tongue flick can add chemical information to what its other senses are telling it.
Next time you meet our mangrove monitor during an encounter, watch that tongue carefully. You’re watching a remarkable sensory system at work — one tiny sample at a time! 💚
