Texas Parks and Wildlife reports snakes emerging from their dens across North Texas as temperatures warm up. Venomous snakes generally have slitted or elliptical pupils, while non-venomous snakes usually have round pupils. However, there are still certain exceptions, so if you encounter a snake, it’s best to stay away. Venomous snakes that call North Texas home include the copperhead, cottonmouth or water moccasin, and the Western diamondback rattlesnake.