The Observer Effect in Herbivory

Abstract

ECOLOGY In field studies of animals, ecologists strive to minimize the potential confounding effects of the presence of the human observer. Now it seems that plant ecologists, too, might have to worry about this problem. In an experiment with six plant species in a temperate grassland community, Cahill et al. monitored the consequences of weekly observer visits on the rate of leaf damage by herbivores. Mean leaf damage from insects significantly decreased in one species and significantly increased in another when plants were visited and handled by observers. Although the mechanisms leading to these effects are not clear (and the effects may be mediated via the eater rather than the eaten), these results suggest that future studies of herbivory, a major ecological subdiscipline, might need to control for the effects of ecologists. — AMS Ecology 82 , 307 (2001).