Humans do not have the ability to see in color, but many animals can only see in black and white. The presence of cone photoreceptors in the eye allows for color vision, different types of cone cells respond to different wavelengths of light, resulting in the perception of different colors.
When it comes to cone receptors, humans and several other primates are trichromats, meaning they have three different types. It was once believed that most mammals could only see in black and white, but this is not the case.
Dichromatic animals, such as dogs and cats, have limited color vision. Monochromatic animals, or those with only one type of cone, can typically see in shades of black, white, and grey.
The number and ratio of rod to cone cells differs between animal species. These factors are heavily influenced by whether an animal is diurnal or nocturnal in terrestrial animals.
Diurnal species, such as humans, have more cone cells than nocturnal species, which have more rod cells to help them distinguish shapes and movement in low light. It include various bats, rodents such as the golden hamster and flat-haired mouse, and the common raccoon.
Most marine mammals are monochromatic; this includes seals, sea lions and walruses, and cetaceans, such as dolphins and whales. Most fish are trichromatic, with good color vision, but there are some exceptions.
