Stable Isotopes, Mercury and Organochlorines in the Eastern Foxsnake (Pantherophis vulpinus) and Eastern Gartersnake (Thamnophis siratilis sistalis) from Southwestern Ontario, Canada.

Road-killed Eastern Foxsnakes (Pantherophis vulpinus) and Eastern Gartersnakes (Thamnophis sirtalis sirtalis) from Southwestern Ontario, Canada, inclusive of samples from Point Pelee National Park (PPNP), were analysed for stable isotopes, mercury and organochlorines. Stable isotopes revealed differences in feeding ecology between the species, with foxsnakes presenting higher trophic status relative to gartersnakes at PPNP. Total Hg did not differ between location, species or body size. Foxsnakes from PPNP were enriched in ∑PCBs and ∑DDTs over gartersnakes but also distinct in chemical signatures from foxsnakes from other locations. 30% of foxsnakes and gartersnakes from PPNP had ∑DDTs/∑PCBs ratios > 2 suggesting foraging ranges of some individuals overlap with former DDT application areas of the park. Hazard assessment revealed high ∑DDT concentrations relative to Canadian tissue residue guidelines for the protection of wildlife in some individual foxsnakes from PPNP, but not for gartersnakes.