Assessing occupancy and functional connectivity of eastern massasaugas (Sistrurus catenatus) across an agricultural-prairie landscape in northern Ohio
Jennifer M. Myers, MS
Advisor: William E. Peterman
The federally threatened eastern massasauga rattlesnake (Sistrurus catenatus) occurs across the Great Lakes region of the midwestern United States in increasingly small and fragmented populations. While massasaugas are relatively well-studied among snakes, much is still unknown about their baseline habitat requirements, as well as how they move across heterogeneous landscapes. One of the most stable remaining populations outside the species strongholds of Michigan and Ontario is found at a wildlife area in northern Ohio.
My research objectives were to: 1) identify land use practices and habitat features that best predict massasauga occurrence at the wildlife area; and 2) determine how the wildlife area is functionally connected for massasaugas given the amount of active agricultural production still taking place on the landscape and the species’ tendency not to travel great distances.
During the 2022 field season, I used adapted-Hunt drift fence technique (AHDriFT) camera arrays and timed constrained visual encounter surveys to assess massasauga occupancy and created single-species integrated occupancy models to establish which covariates best predicted occupancy. Massasaugas were more likely to occupy sites with a higher proportion of open herbaceous habitat, sites with a higher proportion of marginal habitat features like infrequently mowed ditches and field margins, and sites that had been out of agricultural production for a longer time.
I created a series of cumulative kernel density surfaces using three different dispersal kernels to analyze functional connectivity for massasaugas at the wildlife area. I also examined the potential impact of agriculture on connectivity by using three alternative resistance values for agriculture in the resistance surface. The probability of detecting dispersing massasaugas was highest in and around the heavily occupied center of the wildlife area. Using the mean rank for each of the 45 agricultural fields across the nine different density surfaces, I determined which fields dispersing massasaugas would most quickly encounter and potentially colonize if those fields were removed from agricultural production and restored.
The results of these analyses will help facilitate effective and adaptive management for the northern Ohio wildlife area massasauga population and will offer valuable insight into how massasaugas traverse heterogeneous landscapes across their range.