Do mantis shrimp and eagles really see better than we do?
A mantis shrimp has up to 16 kinds of colour detector, and it still can't tell two similar shades apart. Having more is not the same as seeing more.
▶ Start the storyNot in the way the popular stories say. Mantis shrimp and eagles each beat us at something, but neither sees "better" across the board. The mantis shrimp wins on the number of detectors and the range of light it can sense. Eagles win on sharpness, and only some of them do.
Start with the mantis shrimp. Its eyes have between 12 and 16 types of cells, while humans have four. They can perceive light from deep ultraviolet at 300 to far-red at 720 nanometres, plus . It is tempting to conclude that it must see colours we can't imagine.
Mantis shrimp
- 12 to 16 receptor types
- Sees 300 to 720 nm and
- Can't tell apart colours less than 25 nm apart
Human
- Four visual pigments, three for colour
- Lens blocks ultraviolet
The reality is odd. Despite the range, these animals cannot discriminate wavelengths less than 25 apart, so two similar shades look the same to them. A suggested reason is speed: skipping the fine comparison lets a territorial, fight-prone animal decide with little delay. Researchers still debate how its colour system works. A 2022 study failed to find unequivocal evidence for a solely barcode-like system.
Now the eagle. Birds of prey have a very high density of receptors and other adaptations that maximise . Some large , such as the wedge-tailed eagle, have twice the spatial resolution of humans. But many medium and small raptors have a resolution comparable to ours, or lower. Where birds really differ is colour: the eyes of most birds have four types of cone cells, and many see ultraviolet.
So more detectors does not mean finer colour vision, and bird of prey does not mean superhuman sight.
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Recap
More detectors does not mean finer colour vision, and a raptor is not always sharper-eyed than a human.
💡 A trick to remember it · A mantis shrimp's eye is a giant paint box with no fine brush, and 'eagle-eyed' fits the big eagles, not every bird of prey.
Surprising fact · The mantis shrimp's 12 to 16 receptor types don't let it tell similar colours apart.
Connects to
- 🧠 How did two scientists find out how the brain builds shapes from light?
- 🌙 Why does the world turn grey and blurry when the lights go low?
- 👁️ Why don't octopuses have a blind spot like humans do?
- 🐙 How was life discovered thriving where the sun never reaches?
- 🌈 How do our eyes see so many colours with only three kinds of detectors?
- 👁️ Why do octopus eyes look like ours?
- Evolution of the eye
Sources (2)
No source, no claim. Every fact in this lesson (15 claims) cites at least one of these.