Home Biology Physics Records People HMS Marine Life Observatory

 

     Marine Mammals

Harbor Seals, Phoca vitulina richardii

Ring of SealsBetween 250 and 500 harbor seals, both male and female, use the Lovers Point State Marine Reserve beaches to haul out year-round, although numbers vary according to weather conditions and tidal cycles. Hopkins’ West Beach is favored by the great majority. Harbor seals are distinguished from sea lions and elephant seals by short flippers and spotted coats, which range in color from white or light brown to dark gray. Elephant seals likewise lack the external ear flaps possessed by sea lions but are much larger than harbor seals and sea lions.

Harbor seals molt their furry coats once every summer, a process that takes 1-2 months. Harbor seals can live for 25-30 years, but average 12-15 for males, 15-20 for females. They grow to be 5-6 feet long. Males start breeding at 5 years and weigh up to 200 lbs. Females breed at 3 to 4 years and weigh about 150 lbs. Other than the weight difference, males and females look alike. Natural predators of the Pacific harbor seal include orcas (killer whales) and great white sharks.

Harbor seals spend about half of their time in the water and half on land. At night, they forage for fishes, cephalopods, and crustaceans in the waters of the Monterey Submarine Canyon. They can dive as deep as 1,500 feet and hold their breath for up to 35 minutes; the average dive, however, lasts 5 to 8 minutes and is only about 300 feet deep. Harbor seals can sleep in the water by with their bodies submerged and their noses sticking into the air, a resting posture called "bottling."

In Monterey Bay, harbor seals mate in the water during the late spring and early summer. Male seals must compete for females by staging aquatic displays, vocalizing underwater, and sometimes fighting other males. The mating system is unknown but thought to be polygamous.

In March and April, female harbor seals give birth on Hopkins’ protected beaches. Females bear one pup each year and nurse it for 4 to 6 weeks before it is weaned. Pups weigh about 20 lbs and can swim at birth. After a pup is born, the mother will leave the pup on the beach while she forages for food in nearby waters. Unfortunately, some beachgoers mistakenly believe that these pups have been abandoned and will approach, touch, or even take pups away from the beach. All human interaction with seals and pups is harmful and often results in the injury or death of the animal. Seals are protected under The Marine Mammal Act of 1972, making it illegal and punishable by law to "take" marine mammals without a permit. Harassing a marine mammal, or causing any change in its behavior, is considered a "take" under this law.

Since October 2003, John Pearse (University of California, Santa Cruz, Emeritus Professor) has been counting the number of harbor seals he observes from the window of the Pearse house, which is directly across the street from Hopkins Marine Station’s West Beach, and patterns are beginning to emerge. For example, note the scarcity of seals on Hopkins’ West Beach during the month of August each year (see graph below).

Elephant Seals, Mirounga angustirostris

The Northern elephant seal, an extraordinary marine mammal, was hunted to near extinction by the end of the nineteenth century, but its numbers have since recovered. The range of the Northern elephant seal extends over the Pacific coast of North America (Canada, the United States, and Mexico). This animal spends eight to ten months a year in the open ocean, diving 1000 to 5000 feet deep for periods of fifteen minutes to two hours, and migrating thousands of miles, twice a year, to its land-based rookery for birthing, breeding, molting, and rest. Along the central California coast, two rookeries are accessible via Highway 1: The Piedras Blancas rookery, seven miles north of San Simeon, is home to about 15,000 animals. The Año Nuevo rookery, fifty-five miles south of San Francisco and the Golden Gate, is home to about 3,000 animals.

Beginning in the early 1990s, individual elephant seals have been observed occasionally hauling out at the Agassiz Beach at Hopkins Marine Station. Since October 2003, John Pearse (University of California, Santa Cruz, Emeritus Professor) has been counting the number of harbor seals he observes from the window of the Pearse residence positioned directly across the street from Hopkins’ West Beach. It was during these counts of harbor seals that Dr. Pearse began to observe and count elephant seals hauling out on this same beach. Elephant seals are easily distinguished from harbor seals by physical characters; elephant seals are bigger, with longer noses and longer hind flippers, and their coat color is uniform. Equally conspicuous is their distinctive behavior: they flip sand over their bodies and stand up tall while engaging in vigorous pushing matches that appear playful but also prepare them for future battles to establish dominance.

Sea Otters Enhydra lutris

Sea otter and pupOn 19 March 1938, Howard Granville Sharpe was peering through a telescope at the waters below his ranch 13 miles south of Carmel when he spotted ~50 California sea otters in the kelp beds. This sighting was thoroughly astonishing: these few otters, long assumed to have been hunted to extinction, had survived, hidden in kelp beds off remote and rugged shores of Big Sur. Two days later, Sharpe reported the sighting to Hopkins Marine Station.

Over the years, the expanding population extended their range to the north and south of the Big Sur coastline, with otters returning to Hopkins Marine Life Refuge sometime in the 1960's. Since Sharpe’s sighting more than seventy years ago, California sea otters have reoccupied more than 200 miles of coastline, with their principal range now extending from just south of San Francisco to Santa Barbara County. In spring 2009, a survey recorded 2654 sea otters along the central California coast.

In the coastal nearshore ecosystems that it inhabits, the sea otter is, ecologically speaking, a "keystone" species. As such, it is a powerful ecosystem engineer of both the kelp forests and nearby soft-bottom habitats. A top-level predator, the California sea otter feeds almost exclusively on marine invertebrates, including sea urchins, crabs, and numerous molluscs.

Since September 2003, John Pearse (University of California, Santa Cruz, Emeritus Professor) has been counting what he observes from the window of the Pearse house, which is positioned directly across the street from Hopkins Marine Station’s West Beach.

Here is a comparison of the three species mentioned above. These are 30 day averages to even out the days he was not able to make observations. By plotting % Max we are able to see if there is any relationships between the species, as the harbor seals far outnumber otters and elephant seals.

West Beach Mammal Numbers