Marine mammals make up a diverse group of mammal species that rely on the ocean for their existence. In and around Coastal Southern California national parks, marine mammals mainly include pinnipeds (i.e.,seals and sea lions) and cetaceans (i.e., whales and dolphins). During the last century, most populations of marine mammals were nearly decimated by hunting. With the passage of the Marine Mammal Protection Act in 1972, which bans the “take” of any marine mammal, populations have since been making a comeback. Today, living relatively near human activity, pinnipeds and cetaceans are subject to human disturbance such as pollution, collisions with vessels, entanglement in fishing gear, coastal development and habitat degradation, and disturbance from low-frequency noise.
Pinnipeds in Southern California play an important role in the marine food web. As top-level predators, they are sensitive to changes in prey populations and they bioaccumulate persistent organic chemicals that flow from land to sea. Environmental factors, such as oceanic conditions, storm events, climate change, can also affect pinniped abundance, species composition and distribution.
- The Channel Islands have one of the highest diversity of pinniped species in the world. Six species are known to feed and reproduce on the islands. They include the southernmost populations of northern fur seals (Callorhinus ursinus), northern elephant seals (Mirounga angustirostris), California sea lions (Zalophus californianus), harbor seals (Phoca vitulina), Stellar sea lions (Eumetopias jubatus), and the northernmost populations of Guadalupe fur seals (Arctocephalus townsendii).
The oceans in Southern California host an abundance of bottlenose dolphins (Tursiops truncatus), common dolphins (Delphinus sp.), gray whales (Estrichtius robustus), blue whales (Balaenoptera musculus), humpback whales (Megaptera novaeangliae), and other species of cetaceans.