While slaves were generally kept fed and supplied with drink as healthy slaves were more valuable, if resources ran low on the long, unpredictable voyages, the crew received preferential treatment. Slave punishment and torture was very common, as on the voyage the crew had to turn independent people into obedient slaves. Pregnant women on the ships who delivered their babies aboard risked the chance of their children being killed in order for the mothers to be sold. The worst punishments were for rebelling; in one instance a captain punished a failed rebellion by killing one involved slave immediately, and forcing two other slaves to eat his heart and liver.