Estimating abundance of the federally endangeredMitchell's satyr butterfly using hierarchical distance sampling

Abstract

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.

Hierarchical mark‐recapture distance sampling to estimate moose abundance

“…Mark-recapture distance sampling models can accommodate covariates other than distance as part of the detection function (Buckland et al 2004) but generally require that abundance be uncorrelated with these covariates (Sillett et al 2012). Where detection probability is conflated with availability (Schmidt et al 2013), a hierarchical or model-based approach allows density and detection probability to be considered jointly and explicitly (Royle et al 2004, Moore and Barlow 2011, Sillett et al 2012, Hamm 2013.…”

Deriving observation distances for camera trap distance sampling

“…Lepidoptera or Hymenoptera ) if camera resolution is high enough to obtain clear pictures on which species can be identified. Already existing studies applying distance sampling methodology to, for example butterfly counts (Hamm, 2013; Isaac et al, 2011) report that ad hoc species identification combined with distance assignment have proven to be difficult due to the intense effort of butterfly surveys (Isaac et al, 2011). If species can be distinguished phenotypically, CTs could improve both, as species and distance data can be derived from pictures or videos during the analysis.…”

Density and Habitat Relationships of the Endemic White Mountain Fritillary (Boloria chariclea montinus) (Lepidoptera: Nymphalidae)

“…The challenge of efficiently producing unbiased estimates of abundance for mobile organisms, such as butterflies, is not small, least of all because of the difficulty in accounting for individuals that go undetected during surveys. The problem of imperfect detectability has been recognized for many decades and has been addressed extensively in studies of birds (e.g., [9,13]), but methods for estimating detectability have been adopted in studies of butterflies only relatively recently [14,15,16]. Here, we have added to this growing body of literature by demonstrating that using point counts and distance sampling—a common strategy for monitoring bird populations—can be effective tools for studying and monitoring populations of butterflies.…”