Posts Tagged ‘predator’

Depth perception – or why pigeons bob their heads

// September 22nd, 2010 // 1 Comment » // How Things Work, Science Communication, Science in the Movies

I’ve been doing some science tricks lately that show the difference between both eyes. Simple one, close your left eye and line your two pointer fingers up with one 10cm behind the other. Get them so they are exactly in line and you can only see one finger. Now open your left eye and close your right eye. Not so in line anymore.

So we have two eyes on the front of our face, and they both see slightly different images of our world. Our smarty pants brain puts the images together, but it also notices the difference between the pictures and uses it for depth perception.

The same thing is used in 3D cinema, which you can see when you take off the glasses. There’s two pictures, and when an object is supposed to look closer the two pictures are further apart from each other (winces and waits for SexyMan to correct me.)

That’s why most predators have eyes on the front of their heads, so they can gauge the depth from prey. Prey animals usually have eyes on the sides, so they have a bigger range of vision and can see danger coming.

But when I was doing the hole-in-the-hand trick, it just didn’t work for me. I get a hole on the side, like a someone has taken a nibble out of my hand, but not through the middle like everyone else. Is their something wrong with my depth perception? Am I missing out on a 3D world that everyone else in enjoying in full spectroscopic vision?

My saving grace is those stereogram books, where a 3D picture is hidden inside a pattern and you have to go semi-crosseyed to see it. I rock at those books. Oh yeah. I can see the rabbit, or at least a 3D blob that could be a rabbit.

So I’m hoping I have 3D vision. But I wiki’d depth perception anyway, and it turns out there are lots of ways you can check depth besides having two forward facing eyes. Pigeons bob their heads to do it. By moving their heads a little they can see how objects around them move. Objects which are close to them move a lot, and objects that are far away stay stationary. Try it at home!

Leviathan, the ancient marine predator discovered

// July 6th, 2010 // 1 Comment » // Recent Research, The Realm of Bizzare

Deep in a desert in Peru palaeontologists were searching for a skull. Some years ago, teeth thought to belong to a new species of marine animal had been found, but they needed a head to identify it. Hunting in the richest area for ancient sea remains, luck eluded them until the very last day of their travel. Then they found…

Leviathan melvillei. Named after that most fearsome animal the white whale, likened to Leviathan in Herman Melville’s most excellent book Moby Dick. In the old Testament Leviathan was a sea demon, a guardian of the gates of hell. Other cultures thought a dragon or a crocodile, but in modern Hebrew the word means simply whale.

And what a whale is Leviathan.

With 30 cm long teeth it was a dangerous predator. It may have hunted medium-sized baleen whales, who have no teeth and live on plankton. It’s huge teeth would have inflicted deep bites, tearing the baleen whales into pieces. Leviathan lived some 12 million years ago, and looks similar to a modern day sperm whale.

One major difference between the fossil and modern sperm whales is Leviathan had teeth on both jaws. Modern sperm whales only have teeth on the lower jaw, and eat by sucking squid into their mouth. Killer whales are like the funsize version of Leviathan, with teeth on both jaws and violence towards seals. Watch the YouTube documentary to find out more.

They haven’t found the rest of the fossil, so they don’t know how large the whale was, but it was probably around the same size as the sperm whales of today. That’s really big! The largest animal that has ever lived is the blue whale that is still in the ocean now. There are theories that the blue whale is as big as things will ever get.

And so let us take a moment to think of mighty, mad Ahab. That crazy captain who lost his leg to a sperm whale. Wherever you are, Ahab, I be glad you never lived to see this day. The mighty Moby Dick who stole your sanity had but half the dental framework of legendary Leviathan.

Paper published in Nature. Hat tip to Not Exactly Rocket Science.

Update: The name Leviathan was already taken (whoops!) so it has now been renamed Livyatan melvillei, Livyatan being a Hebrew name for large marine monsters.






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