Seven species of seals and sea lions commonly inhabit California coastal waters, four of which are commonly seen in Southern California waters. These animals are of the order Carnivora, suborder Pinnipedia (fin- or feather-footed). This suborder is divided into three families: Otariidae, the Eared seals, which includes sea lions and fur seals; Phocidae, the true seals (hair seals), which includes elephant seals and harbor seals; and Odobenidae, the walruses, which are found only in Arctic waters.

While the various families of pinnipeds share many common characteristics, there are some differences.

The California sea lion, Zalophus californianus, the Northern fur seal, Callorhinus ursinus, and the Guadalupe fur seal, Arctocephalus townsendi, belong to the family Otariidae. They have external ear flaps (pinnae), small tails, and smooth whiskers (vibrissae). They have quadrupedal locomotion (the ability to walk on all fours). They possess nails on the hind flippers. The palmar (bottom-palm) surfaces of the flippers are leathery rather than covered with fur. The Otariids swim primarily with their front flippers, using their rear flippers for steering. Adult males develop sagittal crests (very large foreheads).

Northern elephant seals, Mirounga angustirostris, and Harbor seals, Phoca vitulina, belong to the Family Phocidae. Phocids lack external ear flaps. They have fur on all flipper surfaces and small nails on their digits. They cannot tuck their rear flippers under their bodies for walking. They move by scooting. Most swimming power is gained from the rear flippers.

Typically the animals we treat are brought in as pups and weaners. They are dehydrated and often have parasites. Juveniles that haven’t mastered the technique of fish‑catching are brought in malnourished and dehydrated. Older animals are also treated and may also be malnourished, highly parasitized, dehydrated; have shark bites, propeller wounds, gill net wounds, viral or bacterial infections, cancer, etc. Each animal is treated on a case‑by‑case basis.