How could serpents keep the Jaredites from going into the land southward?

Some readers have thought that the account of the Jaredite troubles with serpents was unrealistic, but other historical accounts show that in certain regions under conditions such as drought and volcanic activity snakes can cause great difficulties even for large groups of people. Before the time of the Persian king Darius, the Neuri people “were forced to quit their country by snakes which appeared all over the place in great numbers, while still more invaded them from the uninhabited region to the north, until life became so unendurable that there was nothing for it but to move out, and take up quarters with the Budini” a neighboring people. Herodotus, The Histories, Book IV:105, in Aubrey de Selincourt, translator, Herodotus: The Histories (London: Penguin, 1972), 248-49. According to Plutarch the Roman general Pompey with his armies tried to invade Hyrcania but “was compelled to go back again for the infinite number of deadly venomous serpents which he met with, being come within three days journey of it.” The Lives of the Noble Grecians and Romans Compared Together By That Grave, Learned Philosopher and Historiographer Plutarch, James Amyot and Thomas North translators (New York: Heritage Press, 1941), 1177. During the reign of the Seljuq ruler Mesud II (1284-1298) his vizier Sadruddin Haldi tried to build a splendid new city on the banks of the Kur river, but “in that area no one could live in the summer because it was swarming with snakes” and after a disastrous flood had to abandon the project altogether at great expense. Fikret Isiltan, Die Deltschunken-Geschichte Des Akserayi (Leipzig: Otto Harrassowitz, 1943), 97-98.