Sight: Animal Senses Series
Catalogue Number: BAM578
Producer: Blue Ant Media
Grade Level: 9 - 12, Post Secondary
Country Of Origin: Canada
Copyright Year: 2017
Running Time: 30
Closed Captions: Yes
Seeing the world is one of the most amazing animal adaptations. Different types of eyes give animals different types of vision, and in some cases they can be extraordinary. Some of the animals featured in this episode are:
Hawks - Birds of prey have the best vision in the world. No other kind of animal gets even close to having the vision hawks and eagles have. In this segment we focus on hawks and their amazing eye adaptations: their telescope-shaped eyes help them spot prey from miles away. A structure called the pecten oculi, neatly organizes the blood vessels inside the eye to prevent them from getting in front of the retina and reducing visual sharpness. Four types of colour receptors allow hawks to see more colours than we can even imagine.
Big Cat Eyes - Some predators have evolved great colour-vision or long distance vision, as a way to spot prey from a distance. Big cats such as lions, tigers, and cheetahs evolved a different kind of eye. They can’t see as many colours as birds or humans, but their night vision is unparalleled. They have a very high density of rods, which are photoreceptor cells in the eye that can detect shapes in very low light situations. On top of that they have a layer of crystals behind the eye called the tapetum lucidum. It reflects light back onto the retina to improve acuity.
Grazing animals - Prey animals such as impalas, zebras, wildebeest and others that live in wide, open spaces are always at risk of being hunted by bigger carnivores. They have had to adapt their eyesight to include as large a field of view as possible.
Great Apes - The vast majority of mammals have two types of cones, which give them a small range of colour vision. Dogs, for example, can only see shades of green and blue. But at some point in their evolution, some primates evolved a third type of cone, which greatly expanded their range of colour vision. We still don’t know when or why this happened but the most accepted theories are that being able to see red and orange helped them find fruits in trees and also see sexual signs from potential mates. Great apes, including humans, have the best colour vision among all mammals in the world.
Compound Eyes - Most insects have poor vision because they mostly rely on their sense of smell to find food and mates. But some insects have managed to turn those poor eyes into amazing hunting tools. Insect eyes evolved in a different way than vertebrate eyes. Instead of one big eye they have thousands of optical units. Each one of them sees a very small part of their environment, but they combine to create a larger image. What they lose in visual sharpness they gain in information processing speed. Compound eyes react to movement much faster than our eyes. Predators like mantis and dragonflies use it to snatch prey out of the air. Other insects also have super fast vision, that’s why it’s so hard to kill a fly.
Mantis Shrimp - The mantis shrimp is a crustacean that’s not really a mantis or a shrimp, it just looks like a hybrid of them. They have compound eyes like many invertebrates and they detect speed almost as well as other great hunters such as mantis and dragonflies. But what set these guys apart are their colour vision and the way they process optical inputs. They have the most types of colour photoreceptors of any animal. They have 12, a lot more than humans, who have 3, and eagles, which have 4. The other interesting thing about mantis shrimp’s eyes is that they do a lot of processing within the eye. Their eye structures hold up to a third of the neurons in their body.
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