Consequences of competition on the time budgets, growth and distributions of three species of terrestrial slugs

Summary The behavioural time budgets of two non‐aggressive slugs and one aggreessive species were evaluated in monocultures or in 2‐way combinations in field cages. The seasonal time budgets of L. maximus, A. ater and A. columbianus in monoculture were remarkably similar despite their strong differences in physiological resource allocation. Similarity in physical design and resource utilization appeared to be more important determinants of behaviour. The time budgets showed distinct seasonal patterns associated with underlying physiological demands for reserve accumulation, sperm acquisition and oviposition. A. ater and L. maximus displayed a definite dispersal phase associated with femalephase maturation. In combination, A. ater and A. columbianus had no detectable effect on one another's time budgets. L. maximus disrupted nearly every category of behaviour in these non‐aggressive species, but its own time budget was not significantly different in the monoculture or in the two combinations, except for minor effects on resting and sexual behaviour. L. maximus appeared to be adapted to maximize behavioural disturbance of interspecific competitors while minimizing intraspecific effects.