In Willy Wonka, Wonka states that the Oompa Loompas were subject to “harsh wastes and fierce beasts… a whangdoodle would eat ten for breakfast”. He then goes on to state that Oompa Loompas were helpless in their environment. Given these traits, we can assume that the Oompa Loompas thrive by procrating quite a bit, basically creating so many that losing ten at a time, several times a day is nothing, otherwise their specie wouldn’t last long.