The population-level effects of an ecosystem engineer: Earthworms affect the behavior of a territorial salamander, Plethodon cinereus

Background/Question/Methods: All organisms affect and are affected by their physical environment. Ecosystem engineers are known to play important roles in the structure and function of the ecosystem at the landscape level so it seems likely that they affect species-specific behavior, intraspecific interactions, and population composition. We conducted two experiments in microcosms to examine whether the earthworm Lumbricus terrestris acted as an ecosystem engineer by providing additional habitat (burrows) for a common, terrestrial salamander species, Plethodon cinereus. We also examined whether the behavioral changes of the non-burrowing, fossorial P. cinereus differed across age classes. Results/Conclusions: 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 a greater number of worms on field plots was correlated with a lower proportion of cover objects being occupied by salamanders (i.e. salamanders were likely underground) and 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, earthworms may have a fairly large impact on above ground faunal communities in the Northeast of the United States.