How does a whale breastfeed?

Like most mammals (aside from Platypuses and Echidnas) dolphins and whales have specialist mammary glands that produce milk. These glands contain specialist milk producing cells.

In a dolphin the mammary glands are situated in sacs on either side of the anus. This allows nursing dolphins to swim behind their mother, insert their beaks into the sacs and latch onto the nipple inside using their tongues and top jaws.