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Kansas Cooperative Fish and Wildlife Research Unit

Robert Harris III (2015)

Robert Harris III (2015)- The Effect of Management Regime on Sex Ratios among Regal Fritillary (Speyeria idalia) Populations in the Central Great Plains (Mentors: Gene Albanese, David Haukos)

The regal fritillary (Speyeria idalia), a large butterfly species once common across the North American prairie ecosystem, has experienced dramatic decline (~99%) and is now considered imperiled. The regal fritillary's range once extended from the Canada border to Oklahoma and east to the Atlantic coast. Eastern populations are nearly extirpated but populations in northeastern Kansas are stable. The primary threats to the regal fritillary are habitat loss, degradation, and fragmentation but recent studies suggest that skewed sex ratios may be a driver of decline among imperiled populations. We surveyed remnant tracts of prairie at the Konza Prairie Biological Station and Fort Riley Military Reservation for regal fritillary adults and established sex for a subset (>25%) of individuals encountered. Surveys were repeated throughout the adult flight period (June to August) and survey areas were stratified by fire return intervals of 20 year (low), 3-5 year (moderate) and 1 year (high) and management regimes of grazing and haying. We also collected vegetation composition and structure data in each adult survey area. Our objective was to assess the overall ratio of males to females, how the ratio changed through time, and the response between male and female density and management regime. Preliminary results indicate that the density of males was significantly greater than the density of females (Student's t-test, p < 0. 01) and this current difference in sex ratio was consistent with observations of the peak male flight (mid-June) and female emergence (late June - July). Male density differed among both fire return interval (ANOVA, p = 0.01) and management regime (ANOVA, p = 0.03). Male density was greatest in areas that had a moderate fire return interval and areas that were grazed. We expect a similar relationship between female density and management regime when surveys are completed. We predict a negative response between female density and haying as hay removal coincides with female emergence. These results suggest that moderate fire return intervals and grazing support greater male regal fritillary density. These findings contrast with current conservation management recommendations (non fire refugia and hay removal) for regal fritillary populations. Management for the regal fritillary should avoid hay removal that coincides with female emergence and aim to increase areas managed using moderate fire return intervals and grazing.