Do All Animals Have Eyelids?
For humans, eyelids are crucial for keeping our eyeballs clean and moist, but many animals have different solutions.
In the water, eyelids are not always necessary. Fish eyes are constantly being moistened by their environment, so they don’t need eyelids. Aquatic mammals like dolphins and whales can blink, but they do so much less often than us.
Back on land, reptiles often lack eyelids too. A snake’s eyes are each covered with a thin, transparent scale, connected directly to the rest of the skin. These scales are fixed into position, keeping the eye safe but preventing any blinking. Some geckos are also unable to blink, and use their tongues to keep their eyes clear of debris.
Insects have compound eyes that are completely different to our own, and
do not need to be kept wet to function properly, so they have no need for eyelids at all.