I wish I could fly like a bird, sprint like a cheetah and see like…a shark? In our “Best in Sight” awards, we bring you the creatures both great and small that have the most astonishing and, often deadly, vision on land, sea and sky. I don’t fancy my odds at a game of hide-and-seek with this lot! Do you?
Anywhere between three to four thousand metres overhead, hawks and buzzards can pinpoint their next meal. It’s an unfair game of catch-me-if-you-can because these Lewis Hamiltons of the sky can reach speeds of 160kpm as they dive towards the Earth. Eagles spot rabbits from several miles away and, with eyesight that is three to four times sharper than our own, their accuracy is outstanding. If only we could have enjoyed such precision when we learned to hang over stairwell banisters, take careful aim and torpedo launch saliva on to victims below. As children, of course.
They say it’s hopeless case trying to swat a fly; although that never stops us turning red-faced from trying eh? While we only have one lens per eye, insects have hundreds. These are called compound eyes and are excellent for detecting motion when paired with an extraordinarily fast ability to process retinal image motion. Think of a dragonfly or tiger beetle and how apt they are at following their prey – a fighter pilot’s dream.
Ever wondered why an owl has the ability to rotate its head 270 degrees? Well, despite being much smaller, owls have eyes almost as big as our own. The downside is that these forward-facing oversized marbles – that can, with certain species, account for almost five per cent of the owl’s bodyweight – are too big to move. But owls are nocturnal and hunt in low-light conditions so they need huge corneas, wide-opening pupils and whopping retinas that are covered in light-sensitive rod cells. It’s no wonder owls deserve a third eyelid: known as the nictitating membrane, this lid is a thin layer of tissue that moves in a horizontal direction to clean the eye’s surface – in other words, a glorified window wiper.
Aussie attitudes to sharks are pretty relaxed – heck, we have to be or we’d never get in the water. But we should in no way underestimate a shark’s hunting ability. Smell is the shark’s most acute sense. Research has shown that from hundreds of metres away, a shark can respond to one to every million part water [source: Shark Trust]. On top of that, special cells in their brain can detect electrical fields and even a twitch can give your hiding place away. As for their sight, sharks have eyes on opposite sides of their head providing an almost 360 degree field of vision. Mirrored crystals located behind the retina (called the tapetum lucidum) allow sharks to see in low light and murky conditions. When the light travels through the retina the crystals reflect the light back on to the retina. Cats also have tapetum lucidum, which explain why both cat and shark eyes appear to glow in the dark. While a shark can see things 10 times better in dim light than a human, they can only see things up to 15 metres away.
Ever see red? Snakes – the likes of pythons, boas and pit vipers – have temperature sensitive organs between their eyes and nostrils. Almost a sixth sense, the radiation that comes in to contact with this heat-sensitive membrane only manages to deliver a blurry image to the snake and edge detectors have to fill in the rest of the detail. Some snakes even have infrared vision which allows them to detect their warm-blooded prey in 3D and launch a viciously accurate attack. Ok, so they can’t quite see through walls but they can detect a mere 0.2 degree heat difference.
Got questions about how to make the most of your eyesight? We can’t guarantee Superman’s thermo vision but you can visit the Sneaking Duck FAQ page for information on prescriptions, measuring your pupil distance and health funds.
Image credits: Thanks to spisharam, gbhone, Hello, I’m Chuck, luc.viatour and zpics for the images off Flickr!