American bullfrogs and Sidewinder rattlesnakes can, and sometimes do, encounter each other. While bullfrogs are ambush predators and will eat a wide variety of prey, including other frogs and snakes, they are also prey themselves. in the real world some animals eat poison which allows them to produce the same poison from their skin example sea bunnies, poison frog, and pitohui, also frogs exposed in chernobyl turn black as black is from melanin in the skin which absorbs radiation.
