Estimating abundance of the federally endangered Mitchell's satyr butterfly using hierarchical distance sampling
Correspondence: Christopher A. Hamm, Department of Ecology and Evolution, University of California at Davis, One Shields Avenue, Davis, California 95616, USA. E-mail: email@example.com
- Estimates of animal abundance are essential to conservation biology and are sorely lacking for many endangered species in the United States of America. This lack of knowledge may disproportionately affect butterflies in the USA, which form the largest group of federally protected insects (20 of 62 species).
- The Mitchell's satyr butterfly, Neonympha mitchellii mitchellii, is a federally endangered species found at 18 highly isolated sites in the Eastern USA. Currently, surveys are conducted by meandering through habitat and recording the number of butterflies observed. These surveys are efficient in terms of staffing and time, but the data from these surveys cannot be used to estimate abundance. Mark release recapture surveys generate estimates of demographic parameters and have been conducted, albeit infrequently, and require high staffing levels and weeks of fieldwork to generate estimates with reasonable error.
- I employed hierarchical distance sampling along line transects to estimate N. m. mitchellii abundance at one site in lower Michigan, USA. This method requires one observer to traverse a series of transects at a walking pace and record the number of butterflies observed and their perpendicular distance to the transect line. My results suggest that this method is as cost efficient as meander surveys, but generates reasonable estimates of butterfly abundance.