Of the 90 amphibian and reptile species and subspecies listed as occurring in the Texas counties encompassing the preserve, 71 are confirmed present, with an additional 19 species that could occur in the Big Thicket. The most diverse group of reptiles are snakes. Sixty-eight snake species have been found in Texas with nearly half of these verified or believed to be living in the preserve. Other types of reptiles present include skinks, lizards, turtles (both aquatic and terrestrial), and the American alligator. Three types of amphibians, including frogs, toads, and salamanders, inhabit Big Thicket National Preserve
Visitors are reminded that alligators can pose some risk to humans. The alligators within the Preserve tend to be secretive and very few human-alligator confrontations have occurred. Snapping turtles can also pose a serious risk if approached and can result in a finger being lost or serious bite. On a similar note, venomous snakes can be found throughout the preserve including rattlesnakes, water moccasins, copperheads, and coral snakes. In most circumstances these snakes are just as determined to get away from you as you are to get away from them. Water moccasins (also called cottonmouths) are probably the most aggressive and least likely to back off as a visitor approaches. Visitors should be careful to watch for any of these reptiles while walking off-trail or while boating in back-water areas. Harassment or killing of any of these highly valued reptiles is illegal.