Animal Vision

What if I told you that you have the ability to see radiation? When we use our eyes to look around we are detecting one type of radiation. That radiation is light! Light is a type of radiation called electromagnetic radiation (ell-ECK-tro-mag-NET-ick ray-dee-AY-shun). There are other kinds of radiation but the only kind we can detect using our eyes is called the visible spectrum (spectrum means range). Humans can only see colours in the visible spectrum, but some other animals can see beyond the visible spectrum. Let’s get an eye-dea of how some of our wildlife neighbours in the Biosphere see their world. 

Owl

Hoo has the coolest eyes in the bird world? It might be owls! In the Biosphere region we have several species of owls, the common species are the Great Horned Owl and the Barred Owl. Owls are nocturnal, meaning they are active at night. They need their eyes to help them see when it’s really dark! 

Owls have big eyes that are tube-shaped, rather than round eyeballs. This unusual shape better collects small amounts of light – and only small amounts of light are available when owls are active at night. This strange shape means that owls can’t roll their eyes within their eye sockets (too bad for sarcastic or annoyed owls!). Instead, owls have flexible necks that let them twist their head around (not 360° but pretty close at 270°) so they can see around them. 

Barred Owl. Photo by Kayla Martin

Dragonfly

Darner Dragonfly. Photo by Kayla Martin.

Dragonflies need to be able to see all around them so they can watch for their insect prey as they zip around in the sky. They also have to be able to see if a predator (like birds such as flycatchers) approaches from any angle.

Dragonflies have two large compound eyes, meaning they eyes are made up of tiny little lenses, each one acting like a single eye. On its own, each lens in the compound eye isn’t very good at seeing, but with thousands together they allow dragonflies to have excellent vision! Dragonflies can see 360° around them… It’s like they’ve got eyes on the backs of their heads, even though it doesn’t look like it! 

Fish

Fish eyes appear pretty similar to those of mammals, birds, reptiles, and amphibians… but looks can be tricky! There is a part of the eyeball called the lens. In fish, the lens is much rounder compared to other animals – almost like the shape of a ball. This gives them better vision underwater. Human eyes are not like this, which is why things look really blurry if we open our eyes underwater. Similarly, fish probably have a blurry view of the world if we take them out of water and into the air. 

Pike fish in aquarium or reservoir under water on fish farm
Comparing side views of a fish and human eyeball.

Ever wonder why fish always have their eyes open? Do they ever sleep? They do sleep, but they do not have eyelids to close over their eyes when they sleep. They don’t need eyelids because in water their eyes won’t get dry and there’s no dust.

Flatworm (Planarian)

The proper name is planarian, but flatworm is much more fun to say! Plus, it’s easy to remember because this creature truly looks like a flattened worm! Flatworms are tiny — smaller than half a centimeter. It’s tricky to spot them without using a microscope. Flatworms live in water, including Georgian Bay and in lakes across Ontario! They usually stick to the underside of rocks, aquatic plants, and dead plant material in the water. 

Freshwater flatworms like the ones in the Biosphere have two eye spots that look a little like silly cartoon eyes. These eye spots are called simple eyes because all they can do is detect light and dark areas. They cannot detect colour or show a clear image of the flatworm’s surroundings. That’s no problem for a flatworm because they have other ways to find food. For example, they can sense chemicals in the water (kind of like how we can smell things in the air).

Flatworm (planarian) under microscope. Photo by Kayla Martin.

Snakes

Scientists are still learning lots about snake eyesight. Snakes probably don’t have great vision: they can see shapes but can’t make out clear, crisp details. Scientists are pretty sure that all snakes can only see blue and green, but not red (humans can see all three). Most snakes can also see ultraviolet (UV) light, which helps them see better in low light. During the day, it can get too bright for snakes because there is lots of UV light and lots of visible light. To help with this, some snakes have a special filter in their eyes so they can block out UV light– like built-in sunglasses!

Some types of snakes can “see” heat. Boas, pythons, and pit vipers have a tiny pit on each side of their face, just in front of their eyes. These pits allow them to sense heat (actually another type of light called infrared light). Pit vipers eat small mammals like rodents, so being able to sense the heat from their prey helps them hunt, especially at night. The only snake in Ontario with this ability is the Massasauga rattlesnake.

How a mouse might look to a snake with pits for sensing heat. Photo by Julius Lab UCSF.

Activities

1. Who am Eye?
Match the eyes with the animal!

2. Think of some of the things you do each day, and think of what animal’s eyes you would like to have for those activities. How would they help you? We’ve filled in one already, but you can add the rest. Add a comment to this blog and let us know what eyes you’d like for one of these activities!

Blog by Kayla Martin, July 2020