Today is World Snake Day. To mark the occasion, Jason G. Goldman of io9 describes how different animals respond to the microgravity that they experience on Vomit Comet aircraft. We've already seen spiders and cats respond to a situation that must be inexplicable to them. What about other species? Goldman writes:
Most animals perceive the weightlessness of microgravity as if they were falling upside down. If you drop a cat from a great height, for example, it will roll over to attempt to land on its feet. This is called the "righting response." In microgravity, this leads to repeated rolling-over.
Scientists have interpreted the repeated rolling-over as a repetitive righting response, since the animal never gets any feedback that the action was successfully executed. This behavioral pattern is common and has been observed for various mammals, frogs, and turtles in microgravity.
Snakes, however, often attack themselves or bunch up. This may be because a snake in microgravity has trouble distinguishing its own body from its surrounding environment:
In this study, the researchers loaded a bunch of snakes onto a Vomit Comet. These are planes that fly in parabolas: as the plane moves over the top of the curve, everything inside is temporarily weightless. At the bottom of the curve, it the pull of gravity actually feels a bit stronger.
Here's a video of one snake, Elaphe obsoleta, in microgravity. In the first parabola, the snake eventually knotted its tail and ceased all other body movements. In the second parabola the snake knotted its whole body and once again ceased moving while in microgravity. This posture was held through the next parabola and in the intervening time between the parabolas.
While the researchers didn't observe the self-attack behaviors seen previously, the knotting behavior that they did observe in many of their snakes still reflects a basic loss of proprioception. When snakes become stressed out, they sometimes bunch together in a group in order to relax. Which, in a way, is exactly what that airborne snake did in microgravity.
In the absence of gravity, it appears as if snakes have a difficulty distinguishing self from non-self.