Can you see me now?
[How different animals see the world]
Birds
Humans have three different cones in their eyes. Humans have a red, blue and green, cone, these cones not only detect the color they were named after but their ranges overlap allowing us to see a range of other colors like orange, yellow, pink, etc. Birds have four different cones, red, green, blue, and UV. So their visible light range is just a little bigger than ours. Below is a demonstration of what birds see, keep in mind that we can’t see UV so the magenta is representing UV that we altered for human demonstration. (1)
(2)
Bees
The visible human spectrum ranges from 390 to 750nm. Nm for those who don’t know means nanometers, this is the measurement we use for the size of the light wave that our eyes can see. Bees along with many insects see waves about 300 to 650nm. Meaning they can’t see the color red but they can see UV. (3)
To see how they see to the world check out this link
Dogs
You may have heard that dogs see black and white. While that’s not completely true, it’s also not too far off. They are red-green color blind, meaning they still see color but they can’t distinguish between something red and something green. Dogs have fewer cones than humans, cones are used to see details like color in high light situations. On the other hand, dogs have more rods meaning they can see better in low light situations (night vision). (4)
Resolution
Now that we saw the different colors that animals see, how about the clarity or resolution they see. Scientists measure this by cycles per degree, humans see about 30 cycles per degree. (8) The wedge-tailed eagle, one of the animals with the clearest vision sees about 140 cycles per degree. That is over four times better than our vision. In contrast, the cleaner shrimp sees about .1 cycles per degree. (6) Unfortunately, we can’t make a picture displaying how the wedge-tailed eagle sees the world, or well we could but our eyes wouldn’t be able to pick up all the detail BUT we can see what the shrimp sees. Check it out here
How do we know this?
Now what I said was cool and everything but how do we know all of this?
Although there are many experiments with many different techniques, here are a couple that helped us determine what animals actually see:
1 We can take a receptor that picks up wavelengths far beyond what our eyes can see, place the eye lens of an animal in front of it, then shoot wavelengths at the lens to see what passes through it. If it passes through, that animal can see that wavelength. (9)
2 Another way researchers have studied animals’ sight was by looking at the photoreceptor in the animal’s eye. They would expose the animal to different light and when the photoreceptors sent signals to the brain they knew that the animal could see that wavelength (3)
Other random facts
- A dragonfly’s brain works so fast that compared to humans it sees movement in slow motion
- Not all animals rely on lightwave for vision, for example, snakes have a third eye that picks up heat signals
- Predators normally have their eyes in front of their heads while prey animals normally have eyes on the side of their head
- While humans have 3 cones in their eyes, mantis shrimp have 12 to 16! I can’t even imagine how colorful and different the world looks for them. (5)
Resources
1 https://news.theearthsite.greatergood.com/how-birds-see-the-world-compared-to-humans/
2 https://www.reddit.com/r/interestingasfuck/comments/dhahdd/human_vs_bird_vision/
