Bayesian Analysis of the Influence of Habitat Characteristics on Occupancy of an Imperiled Watersnake

Document Type


Presentation Date


Conference Name

Society for the Study of Amphibians & Reptiles 58th Annual Meeting

Conference Location

University of Kansas


We explored the use of Bayesian statistics to assess occupancy and habitat preferences of the Copper-bellied Watersnake (Nerodia erythrogaster neglecta), a species that is federally listed as threatened, and is endangered in Indiana, Michigan, and Ohio. Occupancy and habitat data were collected in the area occupied by the federally threatened populations of this species over the summers of 2013 and 2014, with additional occupancy data from the area from 2011 and 2012. The study site was comprised of twelve wetland complexes with historical or recent copperbelly sightings. The goal of this study was to define the link between species occupancy and habitat characteristics. Previous telemetry studies have shown that over a single season, copperbellies often move between several wetlands or wetland complexes and sometimes travel long distances. This level of vagility violates one of the main assumptions of occupancy modeling using Program PRESENCE, that sites remain closed to changes in occupancy status during a surveying season. One of the main benefits of Bayesian analysis is that is allows for dynamic occupancy status during seasons. Other benefits of Bayesian analysis will be briefly discussed, including use of prior data and benefits over frequentist statistical analyses including null and alternative hypothesis testing.



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