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Animals from invertebrates to humans benefit from information conspecifics make available, including information produced inadvertently. While inadvertent social information may frequently be exploited in nature, experiments have rarely been conducted in the wild to examine how such information helps animals in their natural ecology. Here I report a series of field experiments on free-living terrestrial hermit crabs (Coenobita compressus), showing how these asocial invertebrates learn the locations of their most essential resources, food and shelter, using inadvertent cues from conspecific competitors. Crabs have limited abilities to locate resources individually, but as they coalesce on a resource, their aggregation can be noticed by passing foragers, tipping them off about the discovery. Foragers were strongly attracted to experimentally simulated aggregations in which crabs were tethered to the same spot and in which the resources normally found beneath aggregations were excluded. Simulated aggregations of crabs whose shells were removed were likewise attractive, more than even these sought-after-shelters themselves. Experiments that simulated the chemical and visual cues of aggregations independently revealed that foragers oriented to aggregations primarily by sight, cueing in on the jostling competitive activity of the aggregation. Although crabs have not been selected to recruit others to newly discovered resources, their natural ecology has provided a setting where competitors regularly help one another by means of inadvertent social information.

Understanding the process by which limiting resources are incorporated into populations is a major goal of ecology. While many studies have examined this dynamic process using essential resources like homes, few of these studies have involved homes that can be transported by their occupants. This study introduced over a thousand transportable homes into a population of terrestrial hermit crabs Coenobita compressus, animals that carry their homes with them wherever they travel. These new homes were tracked between years to test key predictions about the temporal dynamics the homes would generate, and the spatial and structural changes the homes would undergo as they were used by the population. When moving into new homes, crabs dropped off their old homes directly at the exchange site, and the number of such traded‐in homes peaked rapidly in time. Traded‐in homes were under half the diameter of new homes, a difference apparently magnified by social formations involving vacancy chains. After crabs moved into new homes, they carried the homes away from the exchange site. The following year, these homes were displaced a distance four orders of magnitude times their diameter, thus penetrating extensively through the population. Between years, crabs also remodeled the internal architecture of the homes, creating homes that were more spacious and less of a burden to carry. These results suggest that transportable homes generate novel ecological dynamics along temporal, spatial and structural dimensions, which are a direct consequence of their transportability.