Many animal populations are limited by the availability of life-sustaining resources. A recent study by M.E. Laidre, published in the Journal of Zoology, explored the processes by which resources are incorporated into a population by introducing over one thousand transportable homes into a population of terrestrial hermit crabs Coenobita compressus. The new homes were then tracked between years to test temporal, spatial and structural dynamics. Because empty homes are rare, hermit crabs tend to interact (literally door-to-door) with conspecifics, forming large social aggregations in which many homes are swapped. This was likely to be the cause of the rapid spike in traded-in homes once the introduced homes were discovered. The exchange of homes was accelerated by the creation of vacancy chains, as crabs would drop off their old homes directly at the exchange site. Traded-in homes tended to be under half the diameter of new homes.
After moving to a new home the crabs would move away from the exchange site. The following year, these homes were displaced from the original exchange site by 0.23 ± 0.03 km (range: 0–2.41 km), thus penetrating extensively through the population. Crabs also remodeled the internal architecture by hollowing out the inside to create homes that were more spacious and less of a burden to carry. Remodeling may benefit the crabs, but it is unclear whether it constitutes a net home improvement as remodeled homes had thinner walls, potentially making them more susceptible to breakage or to being crushed by predators. More research is needed to understand how crabs balance these housing costs and benefits. This interesting study suggests that transportable homes generate novel ecological dynamics along temporal, spatial and structural dimensions, which are a direct consequence of their transportability.
By Linda DaVolls