2. At night, if a torch is pointed at a cat’s eyes they reflect light back to the source. Why
does this phenomenon occur?
a. To scare away predators
b. To attract mates
c. To increase sensitivity to low light
d. It is just a side-effect of photoreceptor function
Cat eyes reflect light back to the source at night due to a specialized layer called the tapetum lucidum, which enhances low-light vision. The correct answer is c. To increase sensitivity to low light.
Option Analysis
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a. To scare away predators: Cats are predators, not prey, so this reflection does not serve a defensive scaring function; it aids their hunting.
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b. To attract mates: No evidence links eyeshine to mating signals; the trait evolved for vision, not courtship displays.
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c. To increase sensitivity to low light: Light passes through the retina, hits the tapetum lucidum—a reflective mirror-like layer—and bounces back, giving photoreceptors a second chance to detect it for superior night vision.
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d. It is just a side-effect of photoreceptor function: The reflection is a purposeful adaptation of the tapetum, not incidental to rods/cones alone.
Cat eyes reflect light at night, creating an eerie glow when a torch hits them, thanks to the tapetum lucidum layer behind the retina. This adaptation boosts sensitivity to dim light, vital for cats as crepuscular hunters.
How Tapetum Lucidum Works
Incoming light partially passes the retina’s photoreceptors (rods for low light), strikes the iridescent tapetum, and reflects back through the retina—doubling light exposure for sharper night vision. Excess light exits the pupil as eyeshine, visible from the source. Cats need far less light than humans (about 1/6th).
Evolutionary Benefits
This trait suits nocturnal or twilight-active animals like cats, aiding prey detection and predator avoidance without self-light production. Color varies (green/blue in cats) by species’ riboflavin crystals in the tapetum. Humans lack it, explaining no glow.
Common Myths
Eyeshine isn’t “glowing” (bioluminescence) but reflection; it’s not for scaring foes or mating. In photos, it mimics “red-eye” but shines brighter due to the tapetum.
