Habitat selection in the Common Five-lined Skink near the northern extent of its range
Master of Science
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The study of habitat selection is vital to identify potential threats and to conserve species at risk. The consequences of living in a particular habitat can influence processes beyond the individual with observable effects on populations, species interactions, assembly of ecological communities, and the origin and maintenance of biodiversity. Northern populations of the Common Five-lined Skink (Plestiodon fasciatus) occur primarily in open areas within the eastern deciduous forest of North America. One of two Canadian populations of the Five-lined Skink, the Carolinian population, is currently listed as endangered. The comparative use of macrohabitat types available in northern populations has not been formally described. Furthermore, the relative importance of canopy structure (and associated thermal environment for skinks) when compared to other habitat factors is not well understood. My study asks (1) what macrohabitats are used most by skinks, (2) which habitat factors best predict occupancy, and (3) whether skinks show a gradual or a threshold response to increasing forest canopy cover. I conducted my study at Rondeau Provincial Park in southwestern Ontario. To measure macrohabitat use I completed visual surveys of coverboards placed in four main terrestrial habitat types available at the study site. I compared expected to observed use in each habitat type. To measure how occupancy might be affected by multiple habitat parameters, I completed visual surveys of coverboard transects and collected habitat measurements in the field and using GIS. I used Poisson regression analysis and Akaike Information Criteria to determine which variables contributed to the prediction of site occupancy. I then analysed the same data set using piecewise regression to test for abrupt changes in the relationship between site use and canopy cover. Skinks preferred dune habitat of the main terrestrial habitats available. Skink habitat use was affected most by temperature, canopy cover and moisture. Skinks exhibited a negative threshold response to canopy cover >50% for much of the active season. Habitat loss and the rate of natural succession are concerns for the remaining Endangered Carolinian populations of the Five-lined Skink. Understanding which habitats are used most by this species may assist targeted management efforts to preserve existing isolated populations and to restore areas for future translocations.