The World Through The Eyes of a Snake (That Can Fly!)

I spend most of my days effectively trying to hack the brains of flying snakes (genus Chrysopelea). Nervous systems are incredibly powerful, complicated dynamic control systems, that require sensors and feedback loops to detect the internal and external status of their world. I use behavioral neuroscience to learn about snake vision, and eventually figure out how snakes control their glides using vision. There are a few key questions I’m trying to answer.

What can they see?

I could spend some time here spouting jargon about dimensionality of the vision percept, but suffice it to say that I’m just curious about what their visual system can actually do. If I were to replicate their flying behavior with a cool flying snake robot, how fast would the visual system need to process input? And how high a resolution would their cameras have to be? I ask this question of biological systems, using the Optokinetic Reflex.

If you’ve ever driven by a forest, and tried to follow the trees as they passed, or if you’ve looked at a train, and tried to follow the windows as they passed, then you’ve done the Optokinetic Reflex (OKR). (If you want to try it for yourself, check out this video!)

This smooth pursuit with the eye and/or head, followed by a rapid snap (or saccade) is how brains try to keep the same image held on the retina for as long as possible. This lets visual systems absorb as much information from the scene as they can. Once an object is too small or moving too fast to identify, and the reflex lessens. By changing the size and speeds of the visual scene and comparing the pursuit phase to the rotational speed, I can calculate the visual system limits (and sensitivities!) to both resolution and processing speeds.

Rig with snake-01
Optokinetic drum with snake inside.

These snakes can respond to speeds of up to 99 Hz, and have a spatial resolution that would probably allow them to see a matchstick on the ground from about 2 stories up. Humans would be able to see the same matchstick from about one story higher, but we can only see up to about 50 Hz.

Next, I want to figure out what snakes can see around their head. To do this, I 3D scanned a snake head, and turned it into a 3D graphic.

Do you see what I see?
3D calculation of visual field.

By fitting the eyes with spheres, I can project lines out from the surface of the eye, and map where it intersects. This will help create a 3D map of the visual world, much like the ones used in this study on raptor vision.

journal.pone.0012802.g001.png
3D (top row) and top-down (bottom row) representation of visual fields of different raptors. (Pecten is the feathery comb around the beak.)

What Do Flying Snakes Like To Look At?

We like to look at art, cute cat videos, and Rick and Morty. Snakes have their own version of visually attractive things. The next step in the project is to figure out what about the visual world they prefer to look at–or more specifically, keep in certain areas of their field of vision. When running, biking, or skiing, we will look at the path we’re trying to take as we move through our environment. Using an immersive virtual environment, I can figure out what snakes like to look at while they think that they’re moving.

This project is in the works, and photos and developments will be coming very soon!