"Delta must defeat other Big Daddies and take their Little Sisters, at which point he is given the option to either "harvest" or "adopt" them. Harvesting functions the same as it did in BioShock, whereas with the new "adopt" option, Delta puts the Little Sister on his shoulders, forming a temporary bond with the girl. He then must protect her as she extracts ADAM. The Little Sister will give him some of the ADAM she harvests from Splicer corpses as a reward. After the Little Sister has finished, Delta takes her to a Little Sister Vent, where he will have the choice of saving or harvesting her."