To Catch a Flying Snake

Intrigued by the question of how a limbless, rope-like animal can ‘fly’, Dr Jake Socha films snakes in mid-air motion for his lab. Sometimes, it all goes well; at others, it takes, a ball-point pen to rescue his staffers from fierce snakes

Herpetologists tend to grow up catching critters, particularly of the cold-blooded variety.  I am not a herpetologist.  As a kid I didn’t much care for scampering after beasts, and when it was time to go to the field for the first time to catch flying snakes for my research, I was at a loss.  “How do you catch a snake?”  I asked my fellow grad student, Mike, the only one around who was also working on snakes.  He had a colony of American water snakes in the Westneat lab in the Field Museum of Natural History, and I asked him if he would mind if I could ‘catch’ a captive snake lying in a tank, for training.  “Well, just grab it,” he said with a shrug, suggesting he thought my question dim.  “But grab near the head, so it can’t bite, and grab near the tail as well.”  If not, the frightened snake could emit a foul musk while whipping its tail, spraying a nasty fluid all over the offender.

Heart beating, I reached down into the tank and bravely pulled up a captive water snake.  Success!  I stood there, snake in hand.  As seconds pass, an awful smell overtook us. I looked down to see the snake’s body snapping back and forth, spraying foul funk on my pants.  My lab mates steered well clear of me the rest of the day.

Despite this ‘rigorous’ training, I caught zero snakes in my first field season in Singapore, though partly by design.  I relied on the skill and kindness of savvy locals to snag the snakes they chanced upon.  This passive approach netted a mere four snakes in 10 weeks.

A few years later when I returned to Singapore, I got off my duff and went out and caught the snakes myself.  This turned out to be no trivial task—not only are flying snakes tough to find, but as native tree snakes; they are fast climbers.  If you’re lucky enough to spot one, you then have to get to it quickly, typically by climbing clumsily and barrelling over vegetation.  Usually, you get near only to watch it jump off and glide away.  These snakes have quite a trick up their (armless) sleeves; this ability to glide can make for fast escapes from mere mortal earth-bound predators.

Despite their Houdini-like skill at escape, I managed to catch enough snakes to start my experiments.  The snake-gliding experiments took place in a small open field, ringed by forest.  The basic set-up is simple: a tall scaffolding tower serves as a high place to launch the snakes, who jump off the tower from a branch and glide down to the ground below.  A set of video cameras records it, so we can later recreate points on the snake’s body in 3D.  A form of this technique called ‘mo-cap’, for motion capture, is used in the movie industry to create life-like animations.  My movie-making’s aim was to figure out how the snake moves its body while gliding, a first step towards understanding how a cylindrical, limbless animal can ‘fly’. 

A snake glides by slithering through the sky, looking like a mutant eel swimming in air, moving down at an angle. (Gliders can only fly downward in still air.)  It’s quite unexpected to see how far they can go; your intuition says they should just fall like a rock, or more accurately, a piece of rope.  I’ve seen it hundreds and hundreds of times, but each glide is a revelation. Hats off to you, flying snake.  Really, you just shouldn’t be able to do that, but you are a master of physics, manipulating the airflow over the body to your advantage.  I’m searching for your secrets.

Gathering my crew of volunteers in the open field for snake re-capture training, I was paranoid about the possibility of losing a snake after it glides and lands on the ground.  There is not much room before the field turns to forest, and a fast-slithering snake that made it there would be gone. Hence a lesson in speed; as the snake glides, the snake-catcher starts running. The first concern is to swing a hand down on the back of its body, to pin in it in place, gently enough to avoid harm.  Second, in rapid succession, is to grab the body just behind its head with the other hand.  A snake pinned only by its tail could turn around and bite. Flying snakes are mildly venomous with small fangs in the back of their mouth.  To inject venom, they have to work their jaws forward to get those rear fangs set.  Though these particular bites are harmless to humans, it’s advisable to avoid getting bit.

Over and over, I drilled my troops, emphasising that priority one is grabbing the snake so it doesn’t reach the forest, and second, safely getting the other hand down to secure the head.  My assistants are mostly undergrad science students from the National University of Singapore, eager for a real-life research experience.  All are young and spry, and they take the final message earnestly: whatever you do, get that snake!

The first day of my experiments began well.  Trial 1 was beautiful to watch, and the snake was successfully recaptured.  Then came trial 2.  Kay Yen was up to bat as the runner/catcher.  A university student when he first started working with me, he was earlier working at the Singapore Zoo, though not with snakes. 

My job at the top of the tower was to control the launch, placing the snake on a horizontal branch and guiding it to jump off and glide.  From 10 metres up, I leaned over the rail and watched it glide and land.  Kay Yen raced after the snake and pounced on it in one swift movement, bending down close.  The next instant, I saw his head snap back upright.  He had gotten only one hand on the beast.  Slowly, he turned around, as I stood frozen.  At arm’s length, he was holding the snake’s tail with one hand, then with two.  My heart sank.  The other end of the snake was attached to his face.  At the nose.

Kay Yen tugs on the snake, imploring it to let go.  The snake responds in opposition, stubbornly digging in, ‘walking’ its jaws further up his nose. One jaw is on top and the other in the nostril.  Being a rear-fanged snake, it was trying to move its fangs closer to the flesh, where it could inject a weak venom.  Most flying snake bites I’ve experienced are not like this—the snake doesn’t hold on, because you are not snack-sized.  Bearing the heart of a champion, our current specimen had other ideas. Kay Yen imploringly pulls again, but gently.  He doesn’t want to yank any teeth out of its mouth, which might lead to infection and real harm to the snake. 

Thankfully, the head reptile keeper had been around to watch the opening ceremonies of our experimental festivities.  He runs over to Kay Yen, takes out a ball-point pen, wedges it between nose and jaw, and jams it into the snake’s mouth. The snake gags and immediately lets go.  My heart returns to normal.

Both snake and human are no worse for it, other than being a little shaken up.  The snake rests to glide another day.  Kay Yen sports a ring of tiny, bloody tooth marks on his nose, but these heal quickly and leave no scars.  He takes away a photo to prove his bravery to his kids, and a lesson—if you’re out catching snakes, always keep a pen in your pocket.

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