Posts Tagged ‘prey’

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!

Margay cat of Brasil mimics primates to lure prey

// September 1st, 2010 // 3 Comments » // Science Communication

Altered image, original by Malene Thyssen

At some point in this post I’m going to be tempted to say “copy cat,” so I’m just going to say it now. Copy Cat. There, it’s out of my system, now let’s move on.

On fieldwork in Brasil (so jealous right now) a group of researchers saw a large cat called a margay making some weird noises. It sounded like a pied tamarin pup, a small, supercute primate species, and I recommend you click through that link so you can bask in the cuteness.

In pied tamarin society only the alpha female gives birth, usually to twins, and the pups are looked after mostly by the father. So when the margay made some pup-like mewls, an adult male pied tamarin came down to see what the deal was.


The pied tamarin stayed in the area for a good half hour while the male was keeping an eye out. But as he was watching, the margay made his move. Across some branches… almost… almost… but at the last moment the pied tamarin saw the cat and raised the alarm. All the pied tamarins in the group high tailed outta there quicker than a pirate on shore leave.

In this instance, the margay went without its meal, but a cat using noises to attract prey is unusual. In fact, this was the first time (report came out June 2009) a feline from the neotropical region was found to mimic animal cries. What’s really interesting about the report is that it says local Amazon jungle inhabitants had already told them that the margay and other cats in the area mimicked animals to catch prey. But we don’t accept it scientifically until some scientists witness it and write a report. Just strikes me as unnecessary. Maybe I’m being unscientific, I don’t know.

The margay is an interesting feline. It spends most of its time in trees. It is one of only two cats with the ankles needed to climb down trees head first, the other one being the clouded leopard. It’s been seen dangling from trees hanging by only one foot. I wonder if that observation was made by a scientist?






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