A Little Bit More
Tapetum lucidum is a Latin term that literally means, carpet or tapestry of light. It’s a rare person that hasn’t seen eyeshine in animals but few know why they’re seeing it. This reflective tissue in the eye increases an eyes ability to gather light in minimal light conditions. Although much of the detail may be lost, an animal like a deer or a Raccoon can easily navigate in what seems to humans as “total darkness” without any problem. In fact, cats need only 1/6 as much light as we do to see at night. As the poster points out, no animal can see in total darkness but most nighttime situations have at least “some” light available.
Many mammals have a tapetum lucidum but not the great apes (so that means us too!). Humans do have a wee bit of reflective tissue in their eyes and this is best demonstrated when you see a photograph of someone with “red eye”. However, human eyes are adapted for seeing in daylight and we do not have this specialized adaptation for nighttime vision.
As light passes into and through an eye, various layers of the eye filter the light and causes different colors to be seen in the eyeshine of different animals. So you may see a deep red in a bear’s eyeshine or an orange-yellow in a deer’s glow, a cat may show a greenish tint - eyeshine colors do vary. A few other animals that exhibit eyeshine include sharks, many bony fishes, Alligators, and skunks.
Activities
Science – Eyeshine
Objectives: Experience eyeshine for yourself
Materials: 1 flashlight per person
This is an activity that will best be done in the warmer months although even in winter, if you live where it isn’t too cold, you may be able to perform this activity. If you and/or your family can step outside in some “natural area” at night with a flashlight, you’ll have an opportunity to see some eyeshine firsthand. As you walk near a pond or in a field or park hold a flashlight on the top of your head and direct the light beam ahead in line with your eyesight. Keeping the flashlight in line with your own eyes (up, down or side to side), direct the beam at bushes, the grasses, the pond shoreline etc and look for reflections from the eyes of various animals. Spiders often have reflective eyes and frogs do too. You may come upon a deer or Raccoon or whatever (these will be at a bit of a distance so a strong light may be needed here) and as you direct your light onto the face of the animal, you should be able to see its eyeshine.
Once you find a subject, quietly walk closer and closer until you can get a better look at the subject. I wouldn’t get too close to a large animal but this shouldn’t be a problem with spiders and frogs. You may be surprised at the number of animals that exhibit eyeshine. After all, they need to see as well as possible in their dark environment if they’re going to survive.
Key Concepts
Adaptations and Diversity, Structures and Functions
Questions
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