How cats drink milk without wetting their chins
Researchers have discovered the precise physical mechanism that enables cats to lap up liquids.1,2 It had earlier been thought that they curled their tongue backwards to make a J-shaped curve, and thus ‘ladle’ the fluid into their mouths. But this latest study shows a cat’s tongue actually performs the equivalent of complex mathematical equations to keep two opposing forces in perfect equilibrium.
High-speed digital video shows that only the tip of the upper surface of the cat’s tongue is brought into direct contact with the milk. The cat then rapidly retracts its tongue, drawing a column of milk towards its mouth until the inertia of the column is exactly balanced by the force of gravity pulling it back towards the bowl. That’s when the cat closes its mouth over the top of the column of milk floating in mid-air, snaring its drink.
A domestic cat’s tongue moves at a speed of about one metre per second, lapping about four times a second, with each lap capturing about 0.1 millilitres. Lions and tigers have a lower lapping frequency to maintain the balance between gravity and inertia, maximizing the amount of fluid their larger tongues can capture with each lap.
The researchers were both surprised and delighted at the finding. Sunghwan Jung of Virginia Tech said, “At the beginning of the project we weren’t fully confident that fluid mechanics played a role in cats’ drinking. But as the project went on, we were surprised and amused by the beauty of the fluid mechanics involved in this system.”2,3
References and notes
- Reis, P., Jung, S., Aristoff, J. and Stocker, R., How cats lap: water uptake by Felis catus, Science 330(6008):1231–1234, 2010. Return to text.
- Connor, S., Why the cat that gets the cream is smarter than we thought it was, www.independent.co.uk, 12 November 2010. Return to text.
- For many more examples of the beauty of design features in nature see Sarfati, J., By Design: Evidence for nature’s Intelligent Designer—the God of the Bible, Creation Book Publishers, 2008. Return to text.