Effects of management on butterfly abundance in tallgrass prairie and pine barrens Original Research Article

In transect surveys during 1987–1995 at 104 tallgrass prairies (and open savannas) in Illinois, Iowa, Minnesota, Missouri, North Dakota and Wisconsin, USA and during 1986–1995 at 141 pine barrens in Wisconsin, 137,402 individuals of 122 butterfly species were counted. Twenty percent of individuals and 15% of species were classified as specialists in such habitats, and 26% and 24%, respectively, as more widely distributed ‘grassland species’. Management effects were analyzed as part of stepwise multiple linear regressions for each of 15 specialist and 12 grassland species. Most specialists showed significantly increased numbers associated with less frequent and/or less intrusive managements. However, leaving habitat entirely unmanaged was rarely optimal. Single occasional wildfires were typically more favorable for specialist abundance than regular rotational burning, which often produced very low numbers. Mechanical cutting appeared more favorable than grazing. No management type was clearly favorable for all specialists of a given habitat. The grassland species tended to respond similarly to the specialists except that several favored more frequent and/or more intrusive management and that mechanical cutting was not markedly better for their abundance than grazing, nor wildfire than rotational burning. For conserving specialist butterflies, both consistency of management type within site and deliberate differences in management type among sites of like habitat is desirable.