Swarms of swift scavengers: ecological role of marine intertidal hermit crabs in California

While marine hermit crabs are well known for being omnivorous filter feeders, less is known about the role they may play as active carrion scavengers in intertidal ecosystems. Prior studies have revealed that intertidal hermit crabs can be attracted to chemical cues from predated gastropods. Yet their attraction is usually assumed to be driven primarily by the availability of new shells rather than by food. We conducted field experiments to assess hermit crabs' potential role as generalist carrion scavengers on the California Coast, examining their speed of attraction and the size of the aggregations they formed in response to chemical cues from freshly smashed gastropods and mussels, both of which indicated available carrion. Compared to all other marine species, hermit crabs (Pagurus samuelis, P. hirsutiusculus, and P. granosimanus) were the fastest to arrive at the provisioning sites. Hermit crabs also dominated the provisioning sites, accumulating in the largest numbers, with aggregations of up to 20 individuals, which outcompeted all other scavengers for carrion. Notably, hermit crabs arrived equally quickly for both smashed gastropod and mussel, even though the latter does not offer suitable shells for hermit crabs and even though the former only yields shell-related chemical cues over time frames longer than our experiments. These results thus suggest that shell availability is not the only, or even the primary, reason marine intertidal hermit crabs aggregate at carrion sites; they also aggregate to forage, thereby playing an important role as active carrion scavengers in intertidal ecosystems. Electronic supplementary material The online version of this article (doi:10.1007/s00227-015-2639-3) contains supplementary material, which is available to authorized users.
Author(s): Mark E. Laidre[sup.1] [sup.2] , Alison L. Greggor[sup.1] [sup.3] Author Affiliations: (1) Department of Integrative Biology, University of California, Berkeley, CA, USA (2) Department of Biological Sciences, Dartmouth College, [...]