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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteFrogs catch prey with a partnership: a soft, stretchy tongue cushions the impact, while shear-thinning saliva spreads over the insect and helps hold it during retraction. The saliva then flows again so the frog can swallow. It is not a permanently tacky coating; its apparent viscosity changes with how it is moving.
How does a frog catch an insect with its tongue?
In a 2017 study, Alexis C. Noel, Hao-Yuan Guo, Mark Mandica and David L. Hu combined high-speed filming, measurements of tongue tissue and saliva, and a theoretical model to explain the capture sequence. Their central finding is that adhesion comes from both the tongue’s mechanics and the saliva’s changing flow behavior—not from either one acting alone. The study in the Journal of the Royal Society Interface examined several frog species and used five common leopard frogs (Rana pipiens) for high-speed prey-capture filming; individual results should not be treated as universal measurements for every frog.
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Impact: saliva spreads across the prey
When the tongue hits an insect, its soft surface deforms around the prey. At the high shear rates associated with spreading, the saliva becomes less viscous, allowing it to flow over the insect and into surface texture. That helps increase contact between tongue and prey.
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Retraction: tissue and saliva resist separation
As the tongue pulls back, it stretches and deforms under load. The tissue is viscoelastic: it both changes shape and dissipates energy, cushioning the rapid pull much as a shock absorber cushions a vehicle. Meanwhile, at the lower shear associated with retraction, the saliva is more viscous and helps resist separation.
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Swallowing: saliva flows again
Once the prey reaches the mouth, saliva can flow again, allowing the insect to slide off the tongue and be swallowed. As the paper’s authors put it, “The shear-thinning saliva spreads over the insect during impact, grips it firmly during tongue retraction, and slides off during swallowing.”
What “non-Newtonian” and “shear-thinning” mean
A Newtonian fluid has a viscosity that remains constant under different flow conditions. A non-Newtonian fluid does not: its apparent viscosity depends on how it is being deformed or made to flow. In this case, “shear-thinning” means the frog saliva becomes less viscous as the rate of shear increases. It does not turn into a different substance; the same saliva behaves differently during spreading, retraction and swallowing.
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The study measured frog saliva viscosity reaching a low-shear plateau of 70 Pa·s. The authors compared that value with human saliva as nearly 50,000 times greater. This is a measurement and comparison from the study, not a value established for all frog species or every condition.
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The paper reports several striking figures, but each belongs to a particular observation or comparison in that study.
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| Reported result | What it refers to |
|---|---|
| Under 0.07 seconds | Time for the common leopard frogs in the high-speed filming observations to capture an insect; the authors described it as five times faster than a human eye blink. |
| Up to 12 times gravity | Acceleration measured on the insect during the studied capture observations. |
| 70 Pa·s | Low-shear viscosity plateau measured for frog saliva in the study; the authors compared it with human saliva as nearly 50,000 times greater. |
| 50 times greater work of adhesion | The abstract’s comparison of the studied frog tongue with known synthetic polymer materials, including a sticky-hand toy. It is not a claim about all adhesives. |
| About 60 times greater work of adhesion | The paper’s comparison between tongue adhesion and rigid plates coated with saliva, within its experimental and model analysis. |
These results support a combined-material explanation: a saliva-coated rigid surface alone does not capture the tongue’s performance in the study’s comparison, because the tongue itself deforms and dissipates energy. The authors summarize that role this way: “The tongue acts like a car’s shock absorber during insect capture, absorbing energy and so preventing separation from the insect.”
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why species and animal comparisons matter
The 2017 paper draws on different species and types of evidence: high-speed capture filming used five common leopard frogs, while saliva and mechanical measurements included samples from multiple frog and toad species. Its figures therefore need their experimental context, rather than being presented as fixed properties of every frog tongue.
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Other animal adhesion studies answer different questions. A 2014 study examined adhesion in horned frogs (Ceratophrys sp.) against glass, considering mucus, surface profile and tissue properties (Kleinteich and Gorb, Scientific Reports). A 2016 study concerned chameleons, whose tongue-pad mucus was reported at around 400 times the viscosity of human saliva; that is a chameleon result, not a frog-saliva measurement (Brau et al., Nature Physics).
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