Chipmunks are not known for their night vision. They're a diurnal, or daytime, creature whose eyes work best when the sun is out. The same can be said of humans, too. Chipmunks tend to sleep when the sun sets. When they do come out at night, they're at a grave disadvantage, but they are not totally blind thanks to how their eyes are made.
How Chipmunks See
A chipmunk's eyes work as a means of defense. They and other small mammals tend to experience the world at a higher rate of speed than humans. They must move fast to escape predators, and therefore have to react to stimuli much faster. This includes how their brains translate the sight of, for example, a hawk's shadow into the recognition of what danger that shadow represents. Compared to humans, a chipmunk's view of the world is much faster and larger. It may even be wider thanks to where their eyes are positioned on their heads: their viewing range can be more than a human's 90-degree angle.
What Makes Up the Eye
Mammalian eyes tend to have similar structures inside them, and a chipmunk is no exception. The iris and pupil of the eye aid in gathering up the light outside. The light then passes through the lens on the way to the retina at the back of the eye. Within the retina are what are called rods and cones. Not only do these structures in the eye help to perceive color, but they also help an animal see in darkness. The information is then passed to the optic nerve and into the brain.
Rods and Cones
The rods and cones within the eye are named due to their shapes. The difference between them otherwise is in how they function. Rods work better in low light. They tell the brain basic visual information and catch motion. Cones are for bright light. They give the brain fine details of what is being seen. Chipmunks have many fewer rods than cones in their eyes.
Nocturnal and Diurnal
Chipmunks are diurnal. In other words, they only come out during the daytime. The reason is not because they are blind at night, but because everything is too dark for their main defense system -- their eyes -- to work to their advantage. Nocturnal animals tend to have large eyes with slit pupils of some fashion, as that shape helps them filter out the light. They are specialized for night-time viewing, and may even have a light-boosting mechanism in their eyes called the tapetum. Chipmunk eyes are specialized for use in the daytime. They have smaller eyes with rounded pupils that do not keep the light out well. They can detect motion extremely well and watch for shadows on the ground from airborne predators. If they were out at night, they could not do so.
- Adirondack Ecological Center: Eastern Chipmunk
- NOVA Online: Night Creatures of the Kalahari - The Nocturnal Eye
- Newsweek: Slow Motion; Christopher Dickey
- Discover Nature Close to Home: Things to Know and Things to Do; Elizabeth Lawlor
- Jupiterimages/Photos.com/Getty Images