Gastropodan Mucus

In common English, that's slugs and snails and the locomotive secrections thereof.

We all know they leave those silvery trails, but why? Well, gastropods propel themselves by the ingenious method of using their muscles to generate travelling waves of stress in the thin layers of (foul-tasting, {do not ask me how I know such things}) mucus they lay down.

Mathematicians have calculated that producing the mucus accounts for the largest component in the gastropod's energy budget, more than twenty times the amount of mechanical work used in crawling (which let's face it, isn't very much -though they do have to lug their home around on their backs, I'll give them credit for that). So it behooves them to produce the least amount of mucus they can get away on. This they do using "shear-thinning" - a phenomenon whereby the viscosity of the mucus falls when it is between two surfaces that are moving relative to one another (in this case the ground and their muscular foot). Shear-thinning allows the gastropod to crawl while using the least amount of fluid and thus decreasing the overall energetic cost of locomotion.

So next time you see a schneken trekkin' and it's wallowing in a pool of it's own mucus you'll know it ain't gonna get very far (not any time soon leastways). And if you're into snail racing it'll pay you to bet on the driest one.