Snakes are not normally aggressive towards humans. Snakes bite when they feel threatened. (1.) fast movements because they have poor eye sight. (2.) movement toward their head, no arms or legs to protect them.Remember humans are usually many times larger than snakes. So they normally try to escape. Snakes normally only strike as a last option. Mostly strikes occur when a person is trying to pick one up or trying to kill it. So when you see a snake just stand still.