Watch more: Some dogs use hilariously weird technique to drink water
If you have ever watched a dog drink water, you will know that it can be a splashy and messy affair.
But until now scientists have not been exactly sure why, assuming that canines use their tongues like an inefficient ladle.
High-speed cameras have now revealed that dogs ‘smash’ their tongues against the water to create water columns, which feed into their mouths.
But what makes hunting possible also makes drinking using suction impossible.
Unable to seal their cheeks completely, there is no way for a dog to suck up water, unlike humans, who have ‘complete’ cheeks, which allow us to create negative pressure and suck water into their mouths.
While cats lack suction too, they drink using a two part ‘water entry and exit’ process by placing the tip of their tongue on the water’s surface and rapidly withdrawing it to generate a column of water under their retracting tongue.
Sunny Jung, an assistant professor at Virginia Tech, said: ‘When we started this project, we thought that dogs drink similarly to cats.
‘But it turns out that it’s different, because dogs smash their tongues on the water surface – they make lots of splashing – but a cat never does that.’
When a dog withdraws its tongue from water, it creates a significant amount of acceleration – roughly five times that of gravity – that creates the water columns that feed up into its mouth.
To model this, Professor Jung placed cameras under the surface of a water trough to map the total surface area of the dogs’ tongues that splashed down when drinking.
The researchers found that heavier dogs drink water with the larger wetted area of the tongue.
This finding suggests that there’s a relationship between the water contact area of a dog’s tongue and its body weight, so the volume of water a dog’s tongue can move increases relative to its body size.
In order to better understand how the physiology works, Professor Jung and his colleagues made models of different sized dogs’ tongues and mouths using glass tubes.
This allowed them to mimic the acceleration and water column formation created when a dog splashes its tongue one water’s surface. They then measured the volume of water withdrawn.
The scientists found that the column of water ‘pinches off’ and detaches from the water bath primarily due to gravity.
This means that dogs are smart enough to close their mouths just before the water column collapses back to the bath – just like cats.
They will today describe the findings at the American Physical Society’s Division of Fluid Dynamics (DFD) meeting in San Francisco, California.