A drought occurs. There is no indication that this drought came because a prophet sealed up the heavens, as Nephi, son of Helaman, later did in Nephite history. Nevertheless, the drought comes and disrupts life. One of the interesting aspects is that poisonous serpents appear. If the Book of Mormon took place in Central America, there are a number of poisonous serpents there. In the conditions of a drought, the serpents also need water, and therefore might come closer to human habitation looking for it. Thus, they are in greater contact, and have greater opportunity to endanger the human population.