Pride females synchronize their reproductive cycles, so that when cubs are born, all females can nurture and nurse them. Cubs nurse for six to seven months before weaning. Experts suggest that competition for scarce food leads to a high cub death rate; in the wild, up to 80% of cubs die before reaching maturity. Another possible reason for the high mortality rate is a result of lion breeding behavior. If a new male takes over a pride, he will kill all of the cubs, ensuring that the females will become fertile.