These two words might seem contradictory together but let me clear this up.

Ethical, controlled and regulated hunting is the most efficient method of population control.  

If the number of animals in a specific area reaches or exceeds that area's capacity, the animal population starts to consume more than the environment can provide and the area starts to become depleted. The given population grows on and collapses after reaching a critical level. This happens due to the lack of resources, heavily decreased health of the species as well as many other reasons.