Status of the regal fritillary (Speyeria idalia) and effects of fire management on its abundance in northeastern Kansas, USA

The Regal Fritillary (Speyeria idalia), which once occupied prairies and meadows in North America from the upper Great Plains to the Atlantic coast, has disappeared in recent decades from nearly the entirety of the eastern half of its range and has declined westward. In the Great Plains, where the species is limited to native prairie remnants, several large populations are thought to exist, but patterns of occurrence and abundance in the region have not been described in detail. We surveyed prairies within a three county area of northeastern Kansas using distance-sampling along line transects and found Regal Fritillaries present at 70 of 87 sites. Population density varied considerably among sites but was generally much higher at those that had not been burned in the past year. Despite the loss of >99% of its original prairie landcover and the small sizes of remnants x̄ = 7.1 ha), we estimate that our study area supports a globally significant population of ∼12,000 adult individuals. Given the rapidity of decline of Regal Fritillary populations elsewhere, this study establishes important population benchmarks and a practical protocol for future monitoring efforts.