Gotta Take Care of It Now

This fellow who had spent his whole life in the desert comes to visit a friend. He'd never
seen a train or the tracks they run on. While standing in the middle of the RR tracks one
day, he hears this whistle -- Whooee da Whoee! -- but doesn't know what it is. Predictably,
he's hit -- but, only a glancing blow -- and is thrown to the side of the tracks, with some
minor internal injuries, a few broken bones, and some bruises. 

After weeks in the hospital recovering, he's at his friend's house attending a party, one
evening. While in the kitchen, he suddenly hears the tea kettle whistling. He grabs a
baseball bat from the nearby closet and proceeds to batter and bash the tea kettle into an
unrecognizable lump of metal. His friend, hearing the ruckus, rushes into the kitchen, sees
what's happened and asks the desert man: "Why'd you ruin my good tea kettle?" 

The desert man replies: "Man, you gotta kill these things when they're small."