The main culprit in the wavelike series of amphibian crashes is a chytrid fungus, known as Bd.

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Some trainers teach exercises that involve moving a rope up and down to produce a wavelike motion.

WSJ: What's Your Workout: From a Ball and Basket to a Stick and Some Ice

But gradually this steady wavelike hum was joined by a vague extraneous mutter.

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If you slam the ropes down with enough force, it will produce a wavelike effect that will travel down the ropes and then back up again.

WSJ: What's Your Workout: From a Ball and Basket to a Stick and Some Ice