Patch occupancy and habitat of the hops azure (Celastrina humulus), a rare North American endemic butterfly: insights for monitoring and conservation

Abstract

The hops azure (Celastrinahumulus Scott & D. Wright 1998) is a rare butterfly found along the Front Range of Colorado. Data on the prevalence of the butterfly and its preferred habitats are lacking. To describe the habitat of C.humulus at the southern part of its range, explore what factors impact C.humulus detectability, and estimate C.humulus habitat use along a riparian area known to support it, we conducted an occupancy analysis along the largest riparian system at the U.S. Air Force Academy (USAFA) in Colorado, USA. We used environmental and site-specific covariates to model the probability of detection and the probability of occupancy. Probability of detecting C.humulus was influenced by the amount of cloud cover during sampling, while the probability of occupancy was influenced by the total area of the host plant (wild hops) at the site. Probability of detection was higher during the first visit (69 %) than the second visit (64 %), and the probability of occupancy was higher (77 %) than assumed (30 %). Despite the host plant being patchily distributed throughout the butterfly’s range, the riparian areas at USAFA had a high prevalence of both wild hops and C.humulus. We use the project findings to develop future sampling efforts for the butterfly along tributaries at other locales within the butterfly’s range.