I'm sure they did. Many years ago I used to find fairly dense populations of red legged frogs in certain spots around the northwest. Those spots all had two things in common. Low water pollution, and no bullfrogs. Some of those spots are now infested with bullfrogs and you guessed it, no more red legs around. When the bullfrogs move in, the red legs disappear. Doesn't seem like it has had an effect on the snake population though.

There are other factors though. Red legs are sensitive to pollution, low oxygen, and high water temperatures while bullfrogs can thrive in such conditions. Who knows, the presence of bullfrogs when a wetland is in decline, just might have saved the snakes from disappearing too.