Mountain lions, also known as pumas or cougars, are elusive predators active at night. Their nocturnal habits often raise questions about how they perceive the world in darkness, particularly the appearance of their eyes. When illuminated by a light source, their eyes exhibit a distinctive glow.
The Observed Eye Color at Night
When light strikes a mountain lion’s eyes in low-light conditions, they typically reflect a bright yellow, green, or red glow. This optical effect, known as eyeshine, can also appear in shades of orange. The exact color observed can vary based on factors including the angle of light, the reflective layer’s composition within the eye, and the animal’s age or health.
The Science Behind the Glow
The glowing appearance of a mountain lion’s eyes at night is not due to emitted light, but a reflection of external light, facilitated by the tapetum lucidum, a specialized structure behind the retina. Acting like a biological mirror, it reflects light that has passed through the retina back onto the light-sensitive cells. This gives photoreceptors a “second chance” to absorb limited available light, significantly enhancing the mountain lion’s ability to see in dimly lit environments. The tapetum lucidum is composed of multiple layers of cells, sometimes including photonic crystals. While this adaptation increases visual sensitivity, it can result in a slight reduction in image sharpness.
Mountain Lion Night Vision
The tapetum lucidum is one of several adaptations contributing to a mountain lion’s superior night vision. Their eyes are proportionally large, allowing them to gather more light. They also possess large, round pupils that dilate extensively in low-light conditions, maximizing light entry. The retina of a mountain lion’s eye contains a high concentration of rod cells, which are highly sensitive to low light and motion, with fewer cone cells for color vision and fine detail. These combined features enable mountain lions to see an estimated 6 to 8 times better than humans in low light, and their visual field spans approximately 285 degrees.
Distinguishing Mountain Lion Eyes from Other Animals
While mountain lion eyes typically exhibit a yellow-to-red eyeshine, relying solely on color for identification can be misleading, as color varies and overlaps with other species. Several other characteristics aid in distinguishing their eyes from those of other nocturnal animals. Their eyes are positioned higher from the ground than smaller creatures, and are relatively close-set. Unlike smaller domestic cats, which often have vertical slit pupils, mountain lions possess round pupils.
Observing the movement of the eyeshine can also provide clues about the animal’s identity. For context, deer and elk eyes often shine white, while moose and rabbits typically show red eyeshine. Domestic cats, foxes, and dogs commonly exhibit green eyeshine, though this can also vary.