The Book of Ether says that the Land Northward was plagued with poisonous serpents (rattlesnakes):
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.
33 And it came to pass that the Lord did cause the serpents that they should pursue them no more, but that they should hedge up the way that the people could not pass, that whoso should attempt to pass might fall by the poisonous serpents. (Ether 9: 31, 33)
19 And it came to pass that Lib also did that which was good in the sight of the Lord. And in the days of Lib the poisonous serpents were destroyed. Wherefore they did go into the land southward, to hunt food for the people of the land, for the land was covered with animals of the forest. And Lib also himself became a great hunter. (Ether 10: 19)
The modern day area of Lockport suffered from rattlesnakes as well. Before the Erie Canal was built the American Indians believed Lockport was cursed because the rattlesnakes were so numerous the land was uninhabitable.
These original settlers overcame many hardships to establish their homesteads, removing massive trees and underbrush, clearing the land and avoiding the dangers provided by huge numbers of rattlesnakes. (Lockport web site.)
O. Turner also mentioned this problem in his book Pioneer History of the Holland Purchase of Western New York:
That summer the rattlesnakes were so numerous that they occupied much alarm to the villagers. (p. 655)
“Rattlesnakes in the icy cold near Buffalo New York?”
Yes, there is a unique specie of rattlesnake there in Western New York – proof of a warmer climate during Book of Mormon times before the climate changed – slow enough for the rattlesnakes to adapt.
Venomous Snakes in New York: Distribution and Identification
There are only three species of poisonous snakes living in the wilds of New York (many other kinds may be found in the homes of private individuals and, occasionally, escapes occur!). These are the timber rattlesnake, the massasauga (erroneously called “pygmy rattler”), and the copperhead. All three are uncommon. The timber rattlesnake (listed as “Threatened” by the New York State Department of Environmental Conservation) enjoys the widest range; it is found mainly in the southeastern part of the state, except Long Island and New York City, with scattered populations as far north as Lake George and also along the Southern Tier in western New York. Its populations have been severely reduced, primarily due to bounties and commercial capture for snakeskin products and the pet trade. The massasauga (listed as “Endangered”) occurs in only two locations, both large wetlands. One is located northeast of Syracuse and the other is west of Rochester. This species is the subject of a cooperative research program between researchers at SUNY-ESF and NYSDEC. The copperhead is mainly found along the lower Hudson Valley south of Kingston; it is essentially absent from the Catskills and points further west. (Snakes of New York)
This also confirms what The Book of Mormon says about the Land Northward having them on the western side where the Narrow Neck was that led to the Land Southward.