Did you believe that hermite crabs were always seeking lonelyness? Oh, now, partytime might attract the hermits as well! Read more in the new Early View paper “Eavesdropping foragers use level of collective commotion as public information to target high quality patches” by Mark Laidre. Here is Mark’s own short verison of the paper:
Many people like a party that’s pumping and jostling at just the right amount. Too little commotion and it’s just not attractive. The same seems to hold for terrestrial hermit crabs, which are highly social animals that frequently join aggregations of conspecifics to acquire valuable resources like food or shells. We conducted an experiment to determine what level of commotion from an aggregation would be most attractive to crabs that were eavesdropping outside the aggregation and deciding whether or not to join. The experiment involved creating the equivalent of a puppet show for hermit crabs, with several plugged shells being jiggled at the end of fishing line to simulate different levels of jostling by an aggregation. The jostling of these sham aggregations represented the sort of wild commotion and fighting that goes on when hermit crabs are competing with one another naturally. Indeed, when hermit crabs are contesting highly-quality food resources or when they are in the process of evicting another individual from its shell, their aggregations exhibit especially high levels of natural jostling. In our experiment, we found that eavesdropping hermit crabs were most attracted to the sham aggregations that were jostled at higher rather than lower levels, suggesting that the crabs were using the raucous public commotion as a reliable cue to the presence of valuable resources that were worth competing over. Our experiments provide the first evidence that animals use the behavioral by-products of collectives as a way to increase their own personal foraging efficiency.