How Animals See the World

The most efficient hunter on the planet is not the lion or shark. In fact, lions only successfully capture around 15% of animals they hunt, and sharks catch around 47%. One animal has an astounding capture success rate of 95%: the dragonfly.

Much of its success rate is attributed to its eyesight. A dragonfly’s world looks very different from the human world, so much so that it is impossible for humans to see what it sees.

Dragonflies have compound eyes, which consist of a number of smaller visual units. While houseflies have 6000 compound eyes, dragonflies have up to 30,000. These units present the dragonfly with one picture, not 30,000 little ones. 

The dragonfly eyes wrap almost all around its head, allowing it to see in all directions at once. With this 360 degree vision, it can see without moving its head. This includes behind it as well as underneath it.

The colors humans see are detected by 3 color photoreceptors: red, blue, and green. Most species of dragonflies have many more color photoreceptors, up to 30 in fact. This means they are able to see colors humans cannot even imagine.

As well as being able to see more colors than humans, dragonflies are able to see ultraviolet light. These rays of light from the sun are invisible to humans, however the dragonfly’s ability to see them helps it hunt its prey.

Due to their incredible eyesight, dragonflies experience time differently than humans. Insects like flies and mosquitoes actually move very slowly for dragonflies. They can track a flying object and decide whether it is prey or not in less than 5 hundredths of a second. 

Dragonflies can also see through a polarizing filter, much like when humans wear polarized sunglasses. This ability allows them to view prey that may be hiding underwater even if sunlight is hitting the water.

Dolphins have pretty good eyesight underwater. As their eyes are located on either side of their head, the dolphin’s range of vision is wider than a human's, including being able to see objects located behind them.

It is still relatively unknown how detailed dolphin vision is, or how many colors they can see. However, dolphins have another way to see the world, echolocation.

Echolocation, also called sonar, is the act of sending out sound waves and listening to the changed sound waves bouncing back. Dolphins and bats are 2 species that regularly use echolocation to find food and navigate. 

Recent studies have been looking into the visual picture a dolphin builds using echolocation. It is thought that dolphins are able to detect the shape of prey using echolocation, giving them an extra edge while hunting.

Echolocation is also believed to give the dolphin a 3–D picture. When combined with regular sight, dolphins can determine shape, size, and the internal structure of objects near them. Research suggests that even details such as a diver’s belt can be seen using echolocation.

In order to test dolphins’ echolocation abilities, researchers blindfolded dolphins for a mimic game. The dolphins then had to copy a trainer’s actions.

Despite being blindfolded the dolphins were able to copy the trainer, suggesting that their echolocation skills could build a detailed picture. 

Despite popular opinion, dogs can actually see some color. They have 2 photoreceptors, blue and yellow. This means they are unable to see red and green, so finding a red ball on green grass is a very difficult task for a dog.

What dogs lack in color vision they make up for using another sense; their sense of smell.

Without their acute sense of smell this is what the world looks like to a dog. With just 2 photoreceptors in the eye, a dog sees its surroundings mostly in the colors of blue, violet, and yellow.

This is a stylized version of the world perceived through a dog’s nose. Its nose has over 300 million olfactory, or smell, receptors, and a human nose has only 6 million, meaning its sense of smell is at least 10,000 times better. 

A dog can smell potential prey from long distances. This ability has been harnessed by humans in unusual ways. Researchers studying whale hormones use dogs to find orca feces. Dogs pick up the scent of the feces in choppy water over a mile away. 

When dogs leave their mark on a fire hydrant or a pole they are providing a wealth of information. Like online profiles, the marks provide information including age, sex, whether they have been neutered, their stress levels, and even their social standing. 

A large part of a dog’s brain is dedicated to analyzing smells. This area is about 40 times larger than in a human brain. Dogs are able to smell and remember things that have already passed, allowing them to see back in time.

Snakes in general have relatively poor vision compared to humans. Some species can only detect light, dark, and movement but others have quite keen eyesight. Snakes that live in trees tend to have the strongest eyesight, while burrowing snakes tend to have the weakest.

Several species of snake have independently evolved special heat pits which are used in conjunction with their vision to hunt their prey. 

Pit vipers, pythons, and some boas have evolved a set of infrared sensitive receptors located in the nose of the snake. This allows them to see the body heat of prey species, much like night vision goggles.

These heat pits operate without any input from the eyes. In one study researchers blindfolded snakes and discovered their ability to find prey was not hindered. Researchers also covered the heat pits and discovered that the snake was still able to hunt for prey. 

It is unknown just how detailed the world is when using these heat pits. Spitting cobras can still aim venom at a human's eyes even when blindfolded, suggesting that the heat pits may give the snake more detail than previously thought. 

It is thought that these heat pits are the most sensitive infrared detection receptors on Earth. Learning how they work could be key in developing new technology for use in defense, space exploration, and wildlife management.