Cats defy gravity and use complicated physical properties to drink, according to a study published in Science last week.
Researchers collaborating from the Massachusetts Institute of Technology, Virginia Polytechnic Institute and Princeton University utilized high-speed imaging to study and eventually model the motion of a cat’s tongue as it drinks.
The footage revealed that cats use an unexpected method for lapping. Unlike animals such as dogs, which use a scooping motion to draw liquid into their mouths, cats extend their tongues, curling it sharply at the tip, and touch the water without piercing it. When they retract their tongue they draw a column of water up into their mouth through the properties of water cohesion.
“Drinking presents a challenge to land vertebrates, because fresh water occurs mainly as horizontal liquid surfaces, such as puddles, ponds, lakes or streams, and animals must displace water upward against gravity to drink it,” the researchers wrote.
The method of drinking is especially surprising given that it relies on a non-rigid body part. The researchers pointed out that, like octopus tentacles and elephant trunks, tongues lack “rigid components” and are therefore generally less able to conduct precise movements.
Humans, as well as animals like horses and pigs, have complete cheeks and therefore drink using suction. On the otherhand, animals with incomplete cheeks rely entirely on their tongues to bring water to their mouths. Cats belong to the latter group and their behavioral mechanism for drinking further categorizes them.
“It has some sort of adaptive benefit [if] they’ve managed to evolve in this manner,” Alexander Johnson, an ethologist in the department of Psychological and Brain Sciences at Hopkins, said.
“It highlights the diversity between species . . . Now we have the ability to really look with precision and great detail at how animals behave in particular circumstances. We can look at something like cats licking at a very micro-structural perspective and see how complex and elegant that process actually is.”
The use of modern technology in behavioral research is becoming increasingly prevalent as ethologists attempt to record and understand previously unstudied behaviors. Innovations like high-speed, high-resolution imaging offer a great level of precision and enable researchers to collect large quantities of data regardless of resource or availability.
“The movies allowed us to quantify the lapping kinematics,” the researchers wrote. “The position of the tip of the tongue was tracked over one lapping event and averaged over 11 cycles.”
In order to model the behavior physically, the researchers used fluid dynamics and were able to conclude that the action was being controlled by inertia and gravity, not by viscous and capillary forces. This characterizes cats’ lapping as being part of a larger group of biological topics related to gravity and inertia known as Froude mechanisms.
Looking forward, the researchers noted that their findings may be applicable to a wide variety of fields including soft robotics and other biomechanical models.
Johnson agreed that behavioral research utilizing new technologies is likely to be relevant in other fields.
“That’s one of the great advantages of the current scientific times,” he said. “[We can] really access and examine very basic behaviors, like licking or lapping, and then from that . . . we can provide an idea of how we could model it. And that could provide future direction.”
