Sci usually blogs about things related to health, being a biomedical scientist as she is. But this, this is AWESOME. COMPLETELY AWESOME.
It’s people. Tossing snakes. From towers.
And it made me think so forcibly of the Snake Fight Portion of One’s Thesis Defense (which is brilliant and should be required reading for every grad and post-doc) that I HAD to blog it!
http://www.youtube.com/watch?v=DXAoMiWfk78
(Is this the same lab?)
Socha et al. “Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake” Bioinsp. Biomim., 2010.
Lemme tell you a secret about flying snakes.
Whispesr: flying snakes don’t fly.
What, you knew that already? Awww…:(
Anyway, flying snakes don’t fly, they GLIDE. And so do lots of other animals, like lizards, frogs, and squirrels (the frogs were a surprise to me!). Apparently even ants and SQUID can glide! In fact, the authors include an ENTIRE PHOTOMONTAGE of animals that glide.
(Sadly, I can’t include the whole thing, you’ll have to get access to the paper for that. But I think this is a reasonable portrait of its awesomeness)
Now, with most animals that glide, they move a little at the beginning of the trajectory, spreading out limbs and stuff with extra skin for lift and to change direction, and then glide down diagonally from the start point, getting some extra distance off the launch. Most scientists consider this form of flight to be a little inferior to flight seen in bats and birds, because it doesn’t have all the complex wing motions associated with flight, and of course because they can’t, you know, fly.
But snakes that glide don’t have extra skin and limbs to be throwing around in pursuit of a comfortable flight pattern. Instead, they flatten themselves out to double their normal width, and curve the middle of the body up, creating one big, scaly, writhing “wing”. Once fully launched, in theory a gliding animal will reach equilibrium, but before then, the animal will adjust its shape to get a good glide. Snakes in particular writhe a LOT while they’re in the air. In fact, they flop around so MUCH that the authors of this paper wondered if a snake could ever reach equilibrium during a glide.
So how do you measure this? Well…take a big tower. Take a bunch of video equipment. And take a snake.
This is gonna be fun.
Also, I have to say I love their methods on “animal housing”:
Snakes were housed in plastic aquaria with ad libitum water
and branches for climbing. They were fed geckoes once per
week and given two days to rest after feeding
But more importantly, here’s the setup.
(I think that won’t overwhelm your window…)
Anyway, the view here is from the top of a 15m tower. Cameras point diagonally from this tower and from the target tower, to record the snake’s movement. The 15m tower was the “launch tower” and the other tower was the one the snakes were supposed to aim for, attractively decorated with leafy branches to give them some motivation. They mounted a tree branch on the launch tower to facilitate takeoff. The only major problem is all the trees in the background, which apparently the snakes tried to aim for. They ended up holding up huge black sheets to try and restrict their view to the target tower.
Then, paint your snake. They used dabs of colored paint on specific parts of the snake’s body, each one at an equal distance, so they got good views of where each part of the snake was in the video recordings.
Now sadly, there is not actual snake THROWING. It turns out that these flying snakes will pretty easily take off of their own volition, so all they had to do was release them from a sack on to the branch, and the snakes did the rest, though sometimes a little prodding was required. If the snake didn’t feel like taking off that day, they were put back in the sack. I can only imagine how that must have frustrated the scientists involved, if you have a snake stubbornly clinging to the branch, glaring at you like it’s afraid of heights.
Anyway, they recorded the snakes gliding, and then probably spent the next two years or so analyzing the snakes’ glide trails.
There is a lot of mathematical analysis and beautiful modeling that went on. Unfortunately, I am not at all expert enough to look at that data, so I can only hope that Mark will agree to take it on at some point. But the results are understandable enough even for this mathematical n00b.
It turns out, because of the careful gliding and motion of the snakes, they don’t fall normally (duh), their acceleration actually slows and they move downward at a much more shallow angle than they would if they fell. However, none of the snakes tested actually reached equilibrium in their gliding.
No matter how many times you tested the snakes, all of them (they tested four, but got data from fewer, unfortunately), the animals all moved from side to side during gliding, and they all did it at exactly the same frequency. Not only do they move side to side in rhythm, they move up and down as well. Harder than it looks, try it (try curving your hips from side to side in rhythm as you undulate your body up and down to a different rhythm. See? No as easy as it looks). This suggests they are using an optimum movement here, and suggests that this movement can be mathematically modeled, which is what they set out to do. They did make a model, but it didn’t end up fitting the snake motion exactly (which means more models! And more SNAKE GLIDING!).
Now you might say “awesome! Flying snakes! What’s the POINT?” Well, studying the way animals move, glide, fly, etc, is very important for the development of ROBOTS. Specifically search and rescue robots. You need things that can climb and walk, but you also need things that can FLY. And it might be easier to design a robot that glides rather than flies (fewer potential body alterations). So the idea is to correctly model the way the snake glides, to try and make a robot that can do the same.
Socha JJ, Miklasz K, Jafari F, & Vlachos PP (2010). Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake. Bioinspiration & biomimetics, 5 (4) PMID: 21098961
