is there a difference between colors of a tapedum lucedum among different animals?

Question

example, most cats eyes reflect green and sometimes racoons eyes reflect red, are thier tapedum lucedums diffrent colors or is it just the way the light hits them? i know it sounds dumb but my dad told me when i was little that wild animals eyes reflect red and to stay away from that animal. is there any truth to this? i have been trying to find the reason for this and i haven't been sucessful.

Answer 1

The tapetum lucidum (note the spelling) has different characteristics according to the species. The color reflected depends on its structure but also on the color of the iris.

For instance, some bony fish, crocodiles, and marsupials have retinal tapeta (plural of tapetum). In other vertebrates the tapetum is in the choroid and may be formed by guanine (sharks), cells with refractive material (carnivores, rodents, cetaceans), or extracellular fibers (cow, sheep, goat, horse). The color varies with species, age, and amount of pigmentation in the eye and skin (including fur color); see figure 2 in the paper at the link.

So the answer is yes, there are different colors of tapeta lucida; and no, the red color is not an indication of "wild" animals. In fact, many animals that are diurnal and lack a tapetum lucidum (for example primates, squirrels, birds, pigs) show a red or orange reflection.



See this review article (free access) for more information:

http://www.blackwell-synergy.com/links/doi/10.1111%2Fj.1463-5224.2004.00318.x

Answer 2

I think ms. manners hit the nail on the head. I also think this is a large gray area when it comes to dogs. I think dogs are possessive when they are 'protecting' from things that clearly aren't threats. Then again, it could also be that the dog perceives a threat where we don't--or that the dog is merely protecting themselves while the humans stand by. I also think that dogs can absolutely protect their owners and/or family members. I had an Aussie cut off a bull that was charging at me when I was younger--I certainly viewed that as protection. Same dog also 'protected' us from a dark object in the night once--she wouldn't let us near, and slowly and carefully worked out what it was. Turns out it was a grill cover that had blown over, but that's not the point :)

Answer 3

The tapetum lucidum (Latin: "bright carpet") is a reflecting layer immediately behind, and sometimes within, the retina of the eye of many vertebrates (though not humans); it serves to reflect light back to the retina, increasing the quantity of light caught by the retina. This improves vision in low light conditions, but can cause the perceived image to be blurry from the interference of the reflected light. It is therefore primarily found in nocturnal animals with good night vision, such as cats.



In various species, the tapetum lucidum is responsible for the equivalent of the red-eye effect in humans. In flash photographs, the eyes frequently appear to be glowing in one of a wide variety of colors including blue, green, yellow and pink. Bottlenose dolphins and dogs also have a tapetum lucidum.



The tapetum works roughly on the interference principles of thin-film optics, as seen in other reflective tissues such as butterfly wings (see Blue Morpho). However, different species have different types of structured tissue that lead to different mechanisms of reflective interference (Ollivier 2004). Known tapetum structures include:



Retinal tapetum in teleosts, crocodiles, marsupials and fruit bats

Choroidal guanine tapetum in elasmobranchii

Choroidal tapetum cellulosum in carnivores, rodents and cetacea

Choroidal tapetum fibrosum in cows, sheep, goats and horses