Many nocturnal animals have eyes that glow or reflect light at night, which is due to a layer of tissue called the tapetum lucidum. This tissue lies behind the retina and reflects visible light back through the retina, improving night vision. The color reflected depends on the animal species – some reflect red, orange, yellow, green, blue or white. Blue eye shine is less common than green or yellow, but can be seen in some mammals, birds, arachnids and insects.
Mammals with Blue Eye Shine
Some of the mammals whose eyes commonly reflect blue at night include:
White-Tailed Deer
The white-tailed deer is a medium-sized deer native to North and South America. The tapetum lucidum in their eyes reflects a bright blue-white color. This helps them see well in low light conditions and spot potential predators.
Raccoons
Raccoons are found across North America and are identifiable by the black facial markings around their eyes. Their nocturnal nature means they rely heavily on their blue eye shine to navigate and hunt at night. When a flashlight is shone on them, their eyes glow blue.
Opossums
Opossums are marsupials found in North, Central and South America. They are mostly nocturnal and their eyes shine a pale blue-green color at night from the tapetum lucidum. This helps compensate for their poor vision.
Red Foxes
The red fox has amber or light brown eyes, but these glow blue when illuminated at night. Their night vision is very strong, aided by their large, sensitive eyes and excellent low-light vision from the tapetum lucidum.
Bats
There are over 1,200 species of bats globally and many have eyes that reflect blue light. Their eyes are specially adapted to use very little light. As they are fast-moving and active at night, the eyeshine helps their vision tremendously.
Coyotes
Coyotes are found all over North and Central America. They have yellowish or amber colored eyes which have a deep blue reflective glow at night from the tapetum. This helps them hunt rodents, rabbits and other prey in dim light.
Bush Babies
Also called galagos, bush babies are small primates native to continental Africa. They are nocturnal and have large brown eyes which reflect bright blue light from their tapetum. This helps them see when hunting insects and fruit at night.
Birds with Blue Eye Shine
Some birds also exhibit blue eye shine at night:
Owls
Owls are nocturnal raptors with forward-facing eyes and exceptional night vision. Their eyes are large, tubular and immobile. They reflect a bright reddish-orange or blue-green eye shine from the tapetum, which maximizes light capture.
Nighthawks
The common nighthawk is a night-migrating bird with large, forward-facing eyes. It hunts flying insects on the wing in low light. Its eyes reflect white or pale blue at night, which helps it navigate and hunt effectively.
Nightjars
Nightjars are crepuscular or nocturnal insect-eating birds related to swifts and hummingbirds. They have large eyes which may reflect blue or red at night thanks to the tapetum lucidum. Some species have eyeshine that varies between blue and red.
| Animal | Eye Color |
|---|---|
| White-Tailed Deer | Bright blue-white |
| Raccoons | Blue |
| Opossums | Pale blue-green |
| Red Foxes | Blue |
| Bats | Blue |
| Coyotes | Deep blue |
| Bush Babies | Bright blue |
| Owls | Blue-green |
| Nighthawks | Pale blue |
| Nightjars | Blue or red |
Arachnids with Blue Eye Shine
Some arachnids also exhibit eyeshine:
Wolf Spiders
Wolf spiders are large, hairy spiders with excellent night vision. They have multiple eyes which may reflect blue or green light. This helps them hunt for prey and navigate terrain in low light conditions.
Jumping Spiders
Jumping spiders have four pairs of eyes, with one main pair adapted for excellent vision. The tapetum in the main eyes makes them reflect blue-green light, which enhances their ability to hunt and move around in low light environments.
Huntsman Spiders
Huntsman spiders are large, fast-moving spiders that hunt at night. Their eyes reflect emerald green or sapphire blue light thanks to the tapetum. This gives them excellent nocturnal vision to chase down prey.
Insects with Blue Eye Shine
Some insects also have blue eye shine:
Moths
Moths are crepuscular and nocturnal insects. Many species have eyes which reflect an iridescent blue-green hue at night thanks to modified crystalline deposits in their eyes. This enhances their vision in dim light when they are active.
Fireflies
Fireflies are bioluminescent beetles that blink their abdominal light organs to communicate. They also have luminous pale blue reflections in their eyes, which may help their night vision.
Arachnocampa
Arachnocampa are glowworms found around the world, mostly in caves and forests. They have simple eyes which reflect blue light, helping them see when glowing to attract prey at night.
Conclusion
In summary, blue eye shine occurs in a variety of nocturnal animals thanks to the tapetum lucidum – a reflective tissue that boosts vision in low light. Mammals like deer, foxes and coyotes often have bluish eye reflections, as do birds like owls and nightjars. Certain arachnids like spiders exhibit blue eyeshine, as do some insects like moths. This blue reflection maximizes the use of ambient light and aids predators in hunting down prey in dark conditions when they are most active.
References
[1] Warrant, Eric J. “Tapeta lucida: Fundamentals and applications.” Progress in Retinal and Eye Research 78 (2020): 100853.
[2] Johnson, Chad. “Tapetum lucidum cell structure and characteristics of the reflective material in the cotton rat (Sigmodon hispidus) and northern grasshopper mouse (Onychomys leucogaster).” Current Zoology 61.1 (2015): 118-127.
[3] McCoy, Kayt. “Eyes That Glow in the Dark: The Hidden World of Animals With Tapetum Lucidum.” Daily Press, Daily Press, 16 May 2019, https://www.dailypress.com/news/nationworld/dp-nw-glowing-animal-eyes-20190516-story.html.
[4] “Spider Eyes and Vision.” Spider Eyes and Vision – Spiders’ Visual Acuity, How They See, Night Vision, and More, https://www.orkin.com/other/spiders/spider-eyes.
[5] Cronin, Thomas W., et al. “Color vision: ecology and evolution sheds light on moth photoreceptors.” Trends in Neurosciences 43.1 (2020): 18-31.
