A new study by Researchers at Virginia Tech and Purdue University answers why dogs splash and spill water while drinking. The Study found that dogs splash when they drink because they have the cheeks of a predatory quadruped. As members of the order Carnivora, cats and dogs have incomplete cheeks, which allow them to open their mouths wide to deliver killing blows. But what makes pack hunting possible also makes suction drinking impossible.
Unable to seal their cheeks completely, there would be no way for a dog to suck up water. Conversely, humans have "complete" cheeks, and they drink by creating negative pressure, allowing them to suck water into their mouths and down their throats.
When dogs withdraw their tongue from water, they create a significant amount of acceleration, roughly five times that of gravity that creates the water columns, which feed up into their mouths.
The researchers found that heavier dogs drink water with the larger wetted area of the tongue. This indicated that an allometric relationship exists between water contact area of the dog's tongue and body weight, thus the volume of water a dog's tongue can move increases exponentially relative to their body size.
Researchers found that the column of water pinches off and detaches from the water bath primarily due to gravity. Dogs are smart enough to close their mouth just before the water column collapses back to the bath.