Sources of mortality in the endangered eastern massasauga (Sistrurus catenatus) in Illinois

The identification and management of threats to endangered species are imperative for conservation. Reptile populations are declining globally, yet their secretive nature and a lack of demographic data often make the implementation of conservation strategies difficult. The Eastern Massasauga (Sistrurus catenatus) has been recommended for listing as threatened under the federal endangered species act and listed in Illinois as endangered since 1994. As part of a long-term population monitoring project, we quantified sources of mortality in a population of the Eastern Massasauga using data collected from 2000–2011. Using mortality data amassed during both observational and radio-telemetry studies (2001–2003 and 2009–2011), we classified each mortality event into one of eleven categories. We used Poisson regression to evaluate the impacts of sex, stage-class, season, and study type on mortality. Our results indicate automobiles and predation are the leading sources of mortality, together accounting for over 50% of observed mortalities. We found season and mortality category significantly affected the number of observed mortalities. Most mortalities occur in the summer and fall when snakes are most active. Observational studies detected nearly all the automobile mortality while radio-telemetric studies detected nearly all the predation events. We offer conservation and management recommendations to reduce Eastern Massasauga mortality at Carlyle Lake, which are applicable throughout the range.