Understanding the habitat requirements that best account for the variation in species distribution can help guide management of rare and imperiled populations. The federally endangered Karner blue butterfly (KBB) (Lycaeides melissa samuelis) have declined throughout much of the Midwest in the early 21stcentury due to changes in land use, habitat decline and severe droughts. Ohio populations were restored with captive reared KBB throughout the late 1990’s and early 2000’s with captive rearing efforts ending in 2012. None of the original eight release sites contained KBB after a severe drought in 2012, however a single population established itself in a nearby oak savanna site at an unknown time. Using this naturally colonized site, and eight other oak savanna sites, we examined the extent to which larval host plants, ant abundance, canopy cover and nectar plants accounted for variation in patch use by first and second flight KBB. Results of this study will aid efforts to predict suitable habitat for current and future restorations of this species.
The logistic regression model containing all predictor values for the first and second flights explained 19.1% and 29.1% of the deviance in the KBB occurrence data set respectively. Canopy cover and Lupinus perennis flowering density accounted for 63.7% and 27.3% of the variation in the first flight model respectively with increased canopy cover and lupine flowering density predicting KBB presence. Decreased nectar plant density (47.5% deviance explained), increased canopy cover (22% deviance explained) and increased ant mound density (17.5% deviance explained) were associated with KBB presence in the 2nd flight. All other predictor variables in the second flight model explained < 6% individually. These data demonstrate the importance of canopy cover and the associated thermal protection it may provide to KBB in both 1st and 2nd flights. Increased frequency of drought periods throughout the Midwest may increase the need for heterogeneous landscapes with high amounts of canopy cover that provide thermal refuge. Finally, additional research is needed to understand the full relationship between ants and KBB in order to manage current and future KBB populations more effectively.