Sea Lions and Seals
Brochure of Sea Lions and Seals at Yaquina Head Outstanding Natural Area (ONA) in Oregon. Published by the Oregon State University.
|Oregon Pocket Maps
Sea Lions and Seals in Oregon C hances are, if you’ve spent much time at the Oregon coast, you’ve spotted a sea lion or a seal. Sea lions found on the Oregon coast include the California and the Steller sea lions; the seals you may have seen are most likely harbor seals, although elephant seals are also seasonally present. California Sea Lions (Zalophus californianus) California sea lions are found from Vancouver Island, California sea lion British Columbia, to the southern tip of Baja Califorat Newport’s bay front. The current population along nia in Mexico. They are known for their intelligence, the Pacific coast is approximately 200,000. playfulness, and noisy barking. Their color ranges from Sea lions occasionally get a bacterial infection called chocolate brown in males to a lighter, golden brown in leptospirosis, which affects their kidneys, causing them females. Males may reach 1,000 pounds and seven feet to seek fresh water and come ashore in unusual areas in length; females, which are rarely found in Oregon, as they rest to recover. In 1998 and again in 2000, grow to 220 pounds and up to six feet in length. They large numbers of sea lions were treated for domoic acid have a dog-like face, and at around five years of age, poisoning, a condition caused by harmful algal blooms, males develop a pronounced forehead, a bony bump which causes the animals to have seizures. Other probon top of their skull called a sagittal crest. The top of a lems for California sea lions involve humans. Sea lions male’s head often gets lighter in color with age. These have been found illegally shot and also caught in drift members of the otariid or walking seal family have external ear flaps and large flippers that they use to “walk” or gill nets and other marine debris. on land. The trained “seals” in zoos and aquariums are usually California sea lions. California sea lions are very social animals, and groups often rest closely packed together at favored Steller, or Northern, sea lions are sometimes conhaul-out sites on land or float together on the ocean’s fused with California sea lions but are much larger and surface in “rafts.” They are sometimes seen porpoising, lighter in color. Males may grow to 11 feet in length or jumping out of the water, presumably to speed up their swimming. Sea lions have also been seen “surfing” and weigh almost 2,500 pounds. Females are much smaller, growing to 9 feet in length and weighing up to breaking waves. California sea lions eat squid, octopus, 1,000 pounds. Steller sea lions are light tan to reddish a variety of schooling fish, rockfish, and an occasional brown in color. They have a blunt face and a boxy, salmon. In turn, sea lions are preyed upon by orcas bear-like head. Adult males do not have a visible sagit(killer whales) and great white sharks. tal crest (the bump on the top of their heads) like that California sea lion pups are born south of Oregon of adult male California sea lions. Male Stellers have a on offshore islands in June or July and weigh 13–20 bulky build and a very thick neck that resembles a lion’s pounds. They nurse for at least five to six months and mane, hence the name “sea lion.” up to a year. Mothers recognize pups on crowded rookStellers, named for German naturalist George Wileries through smell, sight, and vocalizations. Breeding helm Steller, are found throughout the north Pacific takes place a few weeks after birth. Males patrol terRim from Japan to central California. Unlike California ritories and often bark during the breeding season to sea lions, Stellers are not often seen in bays or rivers. maintain territories. Steller pups are born on The California sea lion offshore islands from midpopulation has grown during Marine mammals are protected by federal May to mid-July and weigh the 20th century, and the law. It is illegal for unauthorized persons 35–50 pounds. Mothers stay animals can be seen in many to disturb, handle, or feed them. with pups for one to two coastal spots such as the docks Steller, or Northern, Sea Lions (Eumetopias jubatus) Continued weeks before hunting at sea. Then they spend roughly equal amounts of time hunting and nursing pups on land. Pups usually nurse for a year, but some in Alaska continue to nurse for up to three years. Mating occurs 10–14 days after the pups are born. Dominant mature males maintain territories for one to two months and mate with many females. During the breeding season, males do not leave their territories, so they cannot eat. Steller sea lions eat a variety of fishes and invertebrates. Known predators are killer whales (orcas), white sharks, and walrus. The current population of Steller sea lions is about 40,000 along the entire Pacific coast, with about 2,000 in Oregon. There is great concern about this species. The western Aleutian stock has dropped by 80 percent in the last 30 years. In 1997, the western stock in Alaska was listed as endangered and the eastern stock of the continental United States and Canada was listed as threatened. Reasons for this decline are not known. However, researchers believe possibilities include a decline in specific species of fish they eat, competition with commercial fisheries in the Gulf of Alaska, and possible predation by killer whales. Drowning, entanglement in nets, and gunshots are other reasons cited for the Stellers’ decline, but the scale of change makes these possibilities seem unlikely. Stellers are protected under the Marine Mammal Protection Act—which forbids the killing, harming, or harassing of any marine mammal—and the Endangered Species Act. Stellers are susceptible to many of the same diseases as California sea lions, such as leptospirosis and San Miguel sea lion virus, both of which cause a reduction in live births. Harbor Seals (Phoca vitulina) Harbor seals have spotted coats in a variety of shades from silver gray to black or dark brown. They reach five to six feet in length Harbor seal This publication was funded by the National Sea Grant College Program of the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration, under NOAA grant number NA16RG1039 (project number A/ ESG-5), and by appro-priations made by the Oregon State legislature. The views expressed herein do not necessarily reflect the views of any of those organizations. ORESU-G-03-013 and weigh up to 300 pounds. Males are slightly larger than females. They are true seals: crawling and having no external ear flaps. True seals have small flippers and move on land by undulating on their bellies like an inchworm. Harbor seals are found north of the equator in both the Atlantic and Pacific Oceans. In the northeast Pacific, they range from Alaska to central Baja California, Mexico. They favor nearshore coastal waters and are often seen at sandy beaches, mudflats in bays, and on offshore rocks. Oregon harbor seal pups are born in May and June and weigh about 30 pounds at birth. A pup can swim at birth and will sometimes ride on its mother’s back when tired. Pups make a bleating noise that sounds like “maaaa.” After about four weeks, the pups are weaned. Adult females usually mate and give birth every year. They may live 25 to 30 years. Harbor seals spend about half their time on land and half in water, and they sometimes sleep in the water. They can dive to 1,500 feet for up to 40 minutes, although their average dive lasts 3 to 7 minutes and is typically shallow. They eat sole, flounder, sculpin, hake, cod, herring, salmon, octopus, and squid. The total harbor seal population in the eastern north Pacific is estimated to be 330,000. Predators of the harbor seal include sharks and killer whales. Harbor seals are not listed as endangered. People often find harbor seal pups on shore and pick them up, thinking the pups have been abandoned. Usually they are not abandoned; the mothers are just out hunting or watching nearby. Human handling has caused many seals to be orphaned. There are no rehabilitation facilities in Oregon for seals, so if you find a seal pup—or any marine mammal—on the beach, the best thing you can do for it is leave it alone. If you see someone harassing a seal, call the Oregon State Police. © 2003 by Oregon State University. This publication may be photocopied or reprinted in its entirety for noncommercial purposes. Edited by Rick Cooper. Sources: The Marine Mammal Center’s Web site (http://www. tmmc.org/learning/education/pinnipeds/pinnipeds.asp) and Dr. Bruce Mate, professor, Oregon State University Department of Fisheries and Wildlife. Drawings of California sea lion and harbor seal by Herb Goblirsch.