Rabbit Eyes (Why Do They Need A Third Eyelid?)

There are many things that rabbit owners find out when they become a rabbit parent. One of the things that I personally found interesting was that rabbits often sleep with their eyes open. When I did a little research I found out that this was down to the unique structure of the rabbits eye in particular the suprising number of eyelids it has.

Rabbits have three eyelids, the upper and lower eyelids (common in all mammals), and a third eyelid known as a nictitating membrane. This keeps the eye clean so as to be able to clearly see any approaching predator and provides protection to the eye during periods of open eye sleep.

But while this may seem a little strange to humans, there is a good reason that rabbits are built this way and in this article, we are going to find out why.

What is a Nictitating Membrane?

Rabbits have an upper eyelid and a lower eyelid. However, they are also blessed with a third eyelid known as a nictitating membrane.

This sounds pretty scientific, however, when we learn the function of this additional eyelid, we soon see that it serves a very useful purpose.

The nictitating membrane is a translucent or transparent third eyelid underneath the rabbits other two eyelids that moves passively across not more than two thirds of the cornea (the clear outer layer at the front of the eye) when the globe (the eyeball apart from its appendages) is retracted.

Unlike the upper and lower eyelids, the nictitating membrane moves horizontally across the eyeball and is a common feature in fish, amphibians, reptiles, birds and mammals (excluding primates).

rabbit eye nicitating membrane

Why Do Rabbits Need a Nictitating Membrane?

For wild animals, or those descended from wild animals (e.g. dogs) a third eyelid simply acts as protection for the eye. Naturally, animals are more at risk of getting dirt or debris in the eye often given their environment and how they forage for food.

For rabbits, this membrane not only keeps the eyes clean and clear but it also allows them to be constantly on the lookout for potential predators even during periods of sleep and given that these small creatures are right at the bottom of the food chain they need to be alert at all times.

What is really interesting is that while the rabbit is sleeping, the membrane will also keep the rabbit’s eyes hydrated so that when it wakes up, there will be no blurred vision or discomfort.

Nature is a pretty special thing and it is incredible that these animals have developed such intricate functions to keep them alive.

How Often Does A Rabbit Blink?

As the nictitating membrane provides hydration for a rabbit’s eyes. As a result, rabbits do not need to blink anywhere near as frequently as us humans.

Whereas we may blink every few seconds, our pet bunnies might only blink around ten to twelve times an hour.

As we have discussed, this is largely because rabbits are prey animals and need to avoid being made a meal of by the many species of predators that continuously hunt them. Not blinking may seem like a trivial matter, however, seconds count in the wild and this is extra time can be spent staying safe by scanning the surrounding environment.

Why Is My Rabbit’s Third Eyelid Showing?

The third eyelid may be more visible in some rabbits than others, this is most often nothing to worry about and is most likely down to genetics, however, occasionally a third eyelid that becomes progressively more prominent could be an indication of a serious issue, such as a tumor.

If you are at all concerned that concerned your pet may have developed a condition, you should seek veterinary advice as soon as possible. As rabbits are prone to many conditions including cataracts and conjunctivitis, the eyes should be regularly checked for any signs of problems.

Your rabbit’s third eyelid may also protrude from the corner of the eye if it has experienced some sort of trauma. If you keep more than one rabbit together fights (while not likely with bonded rabbits) can also result in eye injuries.

Do Rabbits Sleep With Their Eyes Open?

Something that causes surprise for new rabbit owners is that sometimes, their pets appear to be sleeping with their eyes open. Although this isn’t the case all the time and rabbits will typically only do this when they feel threatened.

In the wild, rabbits will often sleep in a burrow under the ground, well out of the way of predators. But for times when this is not possible or they feel as though they need to be on high alert, they can sleep with their eyes open.

The reason for this is the nictitating membrane that we keep talking about. The rabbit is able to use this transparent eyelid to protect the eye and keep it moist while sleeping. At the same time, the bunny is also able to remain aware of any potential danger that may come its way.

Rabbit Eye Problems

Rabbits are sensitive animals and while they will live many healthy, happy years when properly cared for, they are predisposed to certain health conditions, including those that affect the eyes.

While we would need a much more comprehensive guide to give full details of each of these eye problems some of the most common issues that can affect a rabbit’s eyes are listed below along with some links to reliable sources with descriptions of each:

Wrap Up

Rabbits are delicate animals and the eyes can be another problem area, even with the nictitating membrane providing an extra layer of protection.

While it is important to regularly check your rabbit’s eyes, providing a healthy lifestyle including a good diet, adequate housing, and mental well-being (through companionship and enrichment) will also go a long way to helping to ward off medical issues, especially those that can be attributed to stress.

Further Reading

Eye Inflammation in Rabbits petmd.com

Protruding nictitating membrane medirabbit.com

How well does a rabbit see? northamericannature.com


Darren is the founder and editor at Bunny Advice and has been caring for rabbits for over a decade. He has a passion for helping animals and sharing his experience and knowledge with others.

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