Many endangered species do not have perfect affinity for suitable habitat. For these species, movement behavior is an important component of persistence in small habitat patches. The critical minimum patch size is the minimum area in which individuals stay long enough to reproduce and replace themselves before leaving the patch. We use this theory to evaluate habitat area requirements for an endangered butterfly, the Bartram’s scrub-hairstreak (Strymon acis bartrami). Bartram’s hairstreaks inhabit remnant pine rocklands in southern Florida. Due to its relatively high elevation, pine rocklands were the first areas to be impacted by development, and this habitat now occupies less than 4% of its historic extent. Further, in the absence of historic fire, even protected rocklands are threatened by encroachment of non-native plants and succession to hammock vegetation. With continued pressure to develop small, sometimes degraded, rockland fragments it is challenging to know which fragments could serve as habitat for Bartram’s hairstreaks. We combined movement and demographic data to understand patch area requirements for this butterfly. We used flight path mapping at Navy Wells Pineland Preserve in Homestead, FL to estimate within-patch movement. While this technique has been used successfully for other butterflies, it requires observers to physically follow individuals and it is potentially problematic for species, like Bartram’s, that fly erratically and occupy rough terrain. We used transect count monitoring and INCA (INsect Count Analyzer) software to estimate daily survival of Bartram’s adults on Big Pine Key (the only site for which we had sufficient repeated count data).
Results/Conclusions
We successfully collected 23 flight paths at Navy Wells, split relatively evenly between male (n=8) and female (n=13) individuals (for 2 individuals sex was unknown). Estimated daily survival was 0.097 (95% CI 0.052-0.191). These data were used to estimate diffusion coefficients for these butterflies. We will combine these data to calculate residence time as a function of patch size, and estimate minimum area requirements as a function of possible values for an unknown parameter, the maximum population growth rate. These data inform our knowledge of the basic biology of this endangered butterfly and are a valuable first step in understanding the potential conservation value of small, remnant rockland fragments.