By Cheryl Lock
While we’re used to seeing our cats with their eyes fully closed since they sleep so many hours of the day, whether or not our cats actually blink is a different question entirely.
If you’ve been wondering yourself if your cat blinks, here’s the simple answer—yes, cats do indeed blink. But there’s more to this feline exercise than meets the eye.
Cat Eye Anatomy
In actuality, a cat’s upper and lower lids rarely meet completely, so “blinking” of a cat’s upper and lower lids is often referred to as “squinting” as opposed to outright blinking. This squinting is an important way that your cat keeps her eyes protected. As with humans, a cat’s eyelids will close automatically when something is about to strike her face.
Cats actually have more than just the same two upper and lower eyelids as humans do. They also have an additional third eyelid, technically known as the nictitating membrane, which moves diagonally across the eye starting from its inner corner. This membrane is extremely thin, and it can move very rapidly, faster than the other two eyelids, says Dr. Shelby Neely, director of Clinical Operations at the online veterinary resource whiskerDocs.com. “It moves so fast that it’s very easy to miss,” she says. “In fact, your cat is probably squinting with his upper and lower lids while this membrane is moving, so your cat is ‘blinking’ its third eyelid and you’re missing it.”
How Your Cat’s Eyelids Work
As it turns out, your cat uses her eyelids for multiple purposes. “The purpose of the upper and lower lids is not the same for cats as it is for people, whose lids spread tears and keep the eye moist,” says Neely. “While there are tear glands in the corners of the eyes that are always making tears, cats do not blink their upper and lower lids to clear the tears away. Instead, the tears evaporate after quickly cleaning debris from the eye.”
The third eyelid, however, does help your cat move tears over the surface of her eye, which helps remove debris. “Even for those cats who do not live in a sandy habitat, it may still protect the eyes when a cat is moving through tall grass blades or other potentially dangerous material, or when cats are capturing prey or even just chasing toys,” says Neely.
In fact, according to Neely, this third eyelid probably developed because the practice of keeping cats as human companions began in the Middle East where a great deal of sand gets regularly blown around by strong winds. “The third eyelid could very well be an adaptation that helps to protect cats’ eyes while still allowing them to see to some degree due to the thin membrane,” she says. “This same ability to see through this eyelid is also an advantage during hunting prey, due to the speed with which it moves.”
In addition to protection, cats also use their eyelids for communication. “A cat eye squint—often referred to as a kitty kiss—is a common cat behavior,” says Neely. “Slow ‘blinking’ by a cat—a trance-like, eyes-almost-closed look—is a good sign. [Cats] do this when they are content whether they are alone, with other cats, or with you.”
On the other hand, says Neely, a prolonged, unblinking stare between cats is an intimidating gesture that often signifies dominance. “It can cause a lower-ranking cat to turn around and leave,” she says. “Aggressive cats can use a long-distance stare to control access to the territory they consider theirs.”
So to sum up—yes, cats blink, but probably not in the way that most humans would have guessed. The third eyelid “blinks” probably happen so quickly that you’re likely to miss them, and those upper and lower lid movements that you may have thought were blinks are actually more akin to “squints,” and a sign that your kitty is more than happy with her particular situation at the moment.
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Image: Talita Nicolielo via Shutterstock