An extremely rich and diverse community of marine mammals is found on and around the Channel Islands. Many species of pinnipeds (seals and sea lions) and cetaceans (whales and dolphins) either breed on the islands or feed in the productive waters of the Santa Barbara Channel.
Visitors to the islands often spot huge pods of common dolphins and smaller groups of Risso’s dolphins, and occasionally see the more rare pacific white-sided and bottlenose dolphins. Dolphins feed on anchovies and other small fish, and follow schools of these prey as they move around the channel. Often groups of dolphins will come to a boat and ride the bow wave for long distances. Why do they do this? It may simply be fun, or it may allow them to conserve energy; no one really knows.
During the winter Pacific grey whales migrate between summer feeding grounds in Alaska and breeding areas in Baja, Mexico, passing through the Santa Barbara Channel. Gray whales are often seen by passengers on whale-watching trips between December and March. Other whale species such as humpbacks, blue, orca and fin whales are less common, but can occasionally be seen during the summer when they come to the channel to feed.
California sea lions are often seen by boaters as they haul-out on sea buoys and offshore rocks, and are frequently encountered by divers and snorkelers in the kelp forest. Less often seen by most people are the enormous colonies of sea lions and seals that come to island beaches to breed. At Point Bennett, on the west end of San Miguel Island, hundreds of thousands of northern elephant seals, California sea lions, northern fur seals and harbor seals all breed at varying times throughout the year. The sight is remarkable, and seen by only a few hundred visitors a year who make the trip out to San Miguel Island and then the six mile hike out to the Point, the westernmost point of all the California Islands.
In many ways pinnipeds are as much terrestrial animals are they marine. For much of their lives they haulout on islands and offshore rocks, either for breeding, to give birth or simply to rest. Their presence in large numbers can have significant impacts on terrestrial systems. For example pinniped carcasses, particularly those of non-surviving pups, provide food for seabirds and bald eagles on the islands. And when animals come farther up the shore away from the beaches and the rocks, they can severly impact the vegetation in those areas. Some pinniped species, especially California sea lions and elephant seals, appear to be increasing in abundance while others like harbor seals may be fewer in number around the islands than they were in the past. Significant changes in sea water temperature like those caused by El Nino events appear to have significant effects on pinniped populations around the Channel Islands.