Book 16, Question 98
Why Do Desert Geckos Have Such Big Eyes?
Desert geckos have big eyes because they hunt at night and need to gather every bit of light! Their pupils open wide in the dark, to let in every bit of light. In daylight, they shrink to tiny pinholes.
More fun facts
- Most night animals give up color vision so they can see better in the dark.
- Geckos are unusual because their eyes have no rods, the cells most animals use in dim light.
- Instead, geckos have three kinds of cones, the cells used for seeing colors.
- In tests, nocturnal helmet geckos could tell blue from gray by color alone in very dim light.
- Scientists calculated that the helmet gecko eye is about 350 times more sensitive than human color vision.
- Its large cones and special lens help it see colors in dim moonlight, when people see only shades of gray.
Sources: National Institutes of Health, portal.research.lu.se
Questions kids ask
Can people see colors by moonlight?
Not really. In very dim light our eyes switch to rods, which see only black, white, and gray.