Effects of fire and hay management on abundance of prairie butterflies

Abstract

In transect surveys during summer 1988–1993 at 86 tallgrass prairies in Illinois, Iowa, Minnesota, Missouri, and Wisconsin USA, 80,906 butterflies of 90 species were counted. Individuals were recorded with respect to habitat, type of management (burning or haying), and number of growing seasons since last management. The effects of recent management were analyzed separately for 34 species while controlling for other factors affecting variability in abundance (geography, flight period, weather, yearly fluctuation, vegetation quality and type, patch size, site diversity). While each butterfly species had its own individual response to fire, the prairie specialists (Oarisma poweshiek, Hesperia ottoe, H. dacotae, H. leonardus, Atrytone arogos, Speyeria idalia) showed the most negative effect from fire, which may persist for 3–5+ years. The broader the habitat adaptation, the more over-represented the species tended to be in more recently burned areas and the more under-represented in longer unburned areas. Fire also appeared to affect butterfly abundance based on the species' number of generations per year, vagility, location during fire, and response of their key plants to fire. Specialist numbers were much higher in hayed than burned prairies, while invaders and generalists did not decline markedly with haying. Habitat maintenance with haying is much more favorable for prairie-specialist butterflies than burning.