Ether 9:31

and there came forth poisonous serpents also upon the face of the land, and did poison many people. And it came to pass that their flocks began to flee before the poisonous serpents, towards the land southward, which was called by the Nephites, Zarahemla.

Poisonous snakes came on the land and killed many people. Their animals ran away from the snakes toward the land to the south, which the Nephites called Zarahemla.

Poisonous snakes appeared across the land and killed many people. Their livestock fled south from the serpents, toward the land the Nephites called Zarahemla.