[yipbub]

"These results suggest that diffusive motion [random walks] in Mexican jumping beans does not optimize for finding shade quickly," the authors concluded. "Rather, Mexican jumping beans use a strategy that minimizes the chances of never finding shade when shade is sparse."

[jameshart]

I’m not sure what alternative strategy they are hypothesizing that would find shade more quickly, though?

it seems like the bugs have only one motor function - move in a random direction - and only one input sensor - temperature. What other strategies are available to them than random walk with a probability of movement based on a function of temperature and time?

[mhb]

I don't know either, but is it possible they are concluding that the bugs have only the function "move in a random direction" based on their observations?

If the bugs had the functions 1) move in one direction and 2) turn, then they might have observed a circular or spiral path.

[jameshart]

Put a blindfolded human in a zorb on an uneven patch of desert and I would be impressed if they could manage more than one bounce in the same direction in a row. Not sure what mechanism would enable a jumping bean to reliably bounce ‘forwards’.

[SamBam]

Right, but that conclusion is teleological.

First, they have no evidence that evolution could create a jumping bean that jumps in a straight line. It seems that the direction the bean moves is a function of the uncurling larvae but also the shape of the bean. Possibly such a movement could have evolved, but the authors are presenting this like the random walk improved the larvae's fitness function.

Second, the conclusion that a straight line would find shade quickest, but only for a small percentage of larvae, is obvious and doesn't result in anything scientifically new. Of course if you draw straight lines from any point in all direction, the straight lines that happened to intersect with the shade will be the fastest path to the shade. But just as obviously, heading in a straight line in a random direction is not the most efficient way to find shade.

If they had the freedom to evolve any search strategy possible, there are plenty of search strategies that will uncover shade faster than a random walk. But the larva don't have the ability to select any search strategy they want, they're blind and have no senses besides their current temperature. They have no way of knowing which direction they're facing. Therefore a random walk is simply all that is available to them, it's not a strategy.