Habitat Selection in an Ontario Population of the Snake, Elaphe obsoleta

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Abstract
From late May to mid-Sept. 1982 habitat selection by black rat snakes (Elaphe obsoleta obsoleta) at the Queen''s University Biological Station in eastern Ontario was studied. Radio transmitters were implanted in 4 male and 3 female snakes and used their daily positions as habitat sampling points. The available habitat was also sampled using randomly selected points. The snakes were located 472 times (> 90% success) which produced 107 habitat sample points. All snake example points were separated into active or inactive based on the length of time the snake remained in that position (< or > 7 days, respectively). During the bird breeding season black rat snakes showed a preference for field habitat although in both the field and deciduous forest the snake points were significantly clustered along the habitat interface. Following the bird breeding season, field and deciduous forest habitats were used in proportion to their availability and the preference for the ecotone was no longer found in field samples. Only limited evidence of non-random habitat use was found within habitats with regard to both plant species composition and vegetation structure. Inactive sites were diverse but all were located on the forest-field interface, had open exposure to direct sun and provided shelter for the snakes. Ideal habitat for black rat snakes is a small scale mosaic of field and forest and that their disappearance from other parts of their range in Canada may be related to the disappearance of such mosaics due to land clearing for agriculture.