The influence of habitat provisioning: use of earthworm burrows by the terrestrial salamander, Plethodon cinereus

Studies examining the influence of habitat provisioning by one species on the behavior of other species can provide key insights regarding impacts of ecosystem engineers on the availability of resources to other species. More specifically, an organism’s use of additional habitat provided by ecosystem engineers may affect the interpretation of observational or demographic data. We chose to examine the possible influence of earthworms, as ecosystem engineers, on the behavior of terrestrial salamanders, common forest vertebrates in North America. We conducted two experiments in microcosms to examine whether the earthworm Lumbricus terrestris acted as an ecosystem engineer by providing additional habitat (burrows) for Plethodon cinereus, a common woodland salamander. We also examined whether the behavioral changes of the non-burrowing, fossorial P. cinereus differed across age classes. Adults and juveniles responded similarly, with both adults and juveniles found under cover objects more often when earthworms were absent and using earthworm burrows when available. Our field data supported our experimental data in that greater numbers of earthworms on field plots were associated with a lower proportion of cover objects being occupied by salamanders (i.e., salamanders were likely underground). We found no differences in the response of adults and juveniles to the presence of earthworms. By providing underground habitat for a common terrestrial amphibian, the presence of earthworms may impact demographic studies on salamanders and conclusions drawn from those studies regarding aboveground faunal communities in eastern North America.