When driving at night, many encounter glowing eyes in the darkness. These luminous dots, often seen along roadsides or in wooded areas, belong to deer. This eye shine is not an internal light source, but a remarkable adaptation that helps these animals navigate in low-light conditions.
Common Colors of Deer Eye Shine
The reflection from deer eyes, known as eyeshine, typically appears as a whitish glow. This can often shift to shades of light green or yellowish. While these are the most frequently observed colors, the exact color is not universally fixed. It can also show an orange tint. The exact color seen can vary, indicating that this visual effect is not always uniform.
The Biology Behind the Glow
Deer eyes reflect light due to a specialized structure called the tapetum lucidum, located behind the retina. When light enters the eye and passes through the retina without being absorbed, the tapetum lucidum acts like a mirror, reflecting that light back. This reflection gives photoreceptors a second opportunity to capture the light, effectively doubling the light available to the eye.
This mechanism enhances a deer’s ability to see in dim light, an advantage for crepuscular animals active during dawn and dusk. Deer eyes also contain a higher density of rod cells, sensitive to low light, and have larger pupils than humans, allowing more light to enter. The tapetum lucidum, combined with these adaptations, provides deer with superior night vision, enabling them to detect movement and navigate effectively in near-dark conditions.
Factors Influencing the Perceived Color
The perceived color of deer eyeshine varies due to several external factors. The angle at which a light source, such as a car headlight, strikes the deer’s eye is one influence. Similarly, the observer’s viewing angle also plays a role, as eyeshine is a form of iridescence, meaning its color can shift with changes in perspective.
The type and intensity of the light source also affect the eyeshine’s appearance. For example, a yellowish headlight might make the eyeshine appear more yellow. Minor variations can also arise from the mineral composition within an individual deer’s tapetum lucidum, as well as the animal’s age and health.