Physiology
Pigs and whales are mammals, which means they are warm blooded, feed their babies with milk, have hair and specialized teeth. Pigs and whales belong to the subclass eutheria, which means that they're placental mammals. The pig's bristles are noticeable. A whale is born with bristles, and gray whales are sometimes seen with one or two bristles emerging from their chin. The vestigial teeth of a baleen whale are lost before birth. Pigs and whales come in a range of colors, including black, gray, bluish gray, white or pink and can be spotted or mottled.
Skeletal Structure
Both the pig and the whale have a spinal column and a four-limb body plan. The pig's is seen in its four legs. The whale's forelimbs have become flippers, and its back legs have become so reduced that they're no longer visible. However, the tiny bones are revealed when the whale is skeletonized, as is the vestigial pelvis, which is no longer attached to the spinal column.
Breathing
Pigs and whales both breathe air into lungs and exhale carbon dioxide. For a pig, this is automatic; however, a whale, being completely aquatic, must breach the surface of the water to breathe and expel carbon dioxide. To make this easier, the whale's nostrils have migrated to the top of its head and are now blowholes.
Hearing and Communication
Both pigs and whales have highly evolved inner ears, and excellent hearing, though the whale's ears are simply tiny holes in the sides of its head. The pig's ears collect sound waves and funnel it into the inner ear, as air is a less efficient conductor of sound than water. Both pigs and great whales probably have poor eyesight, as both have eyes on the sides of their heads which restricts their range of vision. Both animals have vocalizations. Pigs have the trademark grunt and squeal, while many whales communicate with clicks, squeals, moans, grunts, whistles or long, complicated, repetitive songs, like the humpback whale.
Social Life
Both pigs and whales are highly intelligent animals. Both whale and pig males fight over females. Both whales and pigs can be very social animals. Beluga whales congregate in pods with hundreds of individuals and killer whales live in hierarchical pods dominated by a matriarch. Female pigs and their young gather in large herds called sounders that can contain up to 100 individuals.