Bulls, Harems, and Pups at Año Nuevo

Female elephant seals and their pups rest at Año Nuevo beach. Photo: Mike Merrit
Female elephant seals and their pups rest at Año Nuevo beach. Photo: Mike Merrit

South of San Francisco, about 20 miles north of Santa Cruz along Highway 1, lies a beach hidden behind sand dunes covered in an undulating meadow of native grasses. From December through March, if you visit, you’ll hear what sounds like a fleet of diesel-powered tractors echoing off the dunes, because this stretch of sand is the breeding ground for northern elephant seals.

This beach is part of a Marine Protected Area called Año Nuevo State Reserve. These marine mammals, which weigh more than 1000 pounds each, migrate thousands of miles to reach this beach every year, where they mate and then give birth.

Male elephant seals can weigh up to 5,000 pounds! Photo: Dan Costa
Male elephant seals can weigh up to 5,000 pounds. Photo: Dan Costa

For a real-life encounter with these marine mammals, you must reserve or join an Año Nuevo guided tour during breeding season, December 15 through March 31. During these months, visitors to Año Nuevo State Park must be on a guided walk to see the seals, and that’s for good reason.

Male elephant seals, called bulls, are extremely protective of their females and will fight other males to ensure exclusive rights to their harems. Weighing in at 3000-5000 pounds during breeding season, these roughly 15-foot behemoths come barreling toward one another on the beach in surprisingly fast undulations.

A bull guards one of the females in his harem. Photo: Dan Costa
A bull elephant seal guards one of the females in his harem. Photo: Dan Costa

What’s That Sound?

As the bull rears up, with his two-foot trunk-like proboscis flapping, he lets out a series of deep, guttural bellows in rhythmic bursts. They sound somewhat like a series of loud farts and burps in an echo chamber or a diesel engine from the early 1900s.

Wildlife biologists once thought that the louder the bellow, the larger and stronger the bull, so the encroaching male could determine by sound alone whether he was a match for his opponent. Although this theory isn’t far off, recent research by Caroline Casey and Colleen Reichmuth at the University of California Santa Cruz has revealed that each male has a distinct “clap-threat call.” If two males have fought before, they recognize each other by this call. This gives the challenger a chance to back down from starting a fight with an opponent he knows he can’t beat.

Females lose 16.5lbs per day while nursing their pups. Photo: Dan Costa
Females lose 16.5 pounds per day while nursing their pups. Photo: Dan Costa

Mom of the Year

After the females give birth, the pups must be nursed for three weeks straight. During this time, the mothers lose 30-40% of their body weight. That works out to 16.5 pounds per day! As soon as her pup stops suckling, the emaciated female becomes sexually receptive, so males try to mate with her as she makes her way to the ocean for a feast of fish after a nearly month-long fast.

This map shows the diving pattern of an individual female elephant seal foraging on Pratt Seamount in the northeast Pacific. Image: From the collection of Dan Costa, adapted from his publication in Marine Mammal Science, 2011 (see below for complete citation).
This map shows the diving pattern of an individual female elephant seal foraging at Pratt Seamount in the northeast Pacific. Image: From the collection of Dan Costa, adapted from his article in Marine Mammal Science, 2011

Deep Divers and Long-Distance Swimmers

Out in the ocean, both the females and males dive to depths of 1500 feet, on average, and can stay submerged for up to two hours in search of bottom-dwelling fish. The deepest dive recorded was 5778 feet, which is more than a mile.

A female northern elephant seal in the ocean where she spends 10 months of the year foraging. Photo: Dan Costa
A female northern elephant seal in the ocean where she spends 10 months of the year foraging. Photo: Dan Costa

When the northern elephant seals aren’t overrunning the beach at Año Nuevo, they spend most of the year in the open ocean foraging for food. For one month, they rest on a sandy beach during a catastrophic molt. They shed all of their fur at once and grow a new coat. Females and males travel thousands of miles apart on their semiannual migrations. They frequent different feeding areas but return to the same beaches to mate and molt. In one year, females travel approximately 11,000 miles and males travel about 13,000 miles.

Tracks of male (red) and female (yellow) northern elephant seals on their foraging trips to the North Pacific and Gulf of Alaska. Animals were tagged by the Tagging of Pacific Pelagics (TOPP) research group at Año Nuevo (image courtesy of Dan Costa/UCSC).
Tracks of male (red) and female (yellow) northern elephant seals on their foraging trips to the North Pacific and Gulf of Alaska. Animals were followed by the Tagging of Pacific Pelagics (TOPP) research group at Año Nuevo. Image. Courtesy of Dan Costa/University of California, Santa Cruz

Although they were nearly hunted to extinction in the 19th century for the oil in their blubber, their population is now an estimated 150,000. In California, their population continues to grow each year by 20-30%. There are multiple factors involved in that increase, but one is protection under the Marine Mammal Act since 1972 and another is the grizzly bear’s disappearance from the entire state because they were hunted to extinction. With no more bear attacks to threaten them while they are breeding, nursing, and molting on the beach, the seals have thrived.

Females and their pups in the water just offshore at Año Nuevo Beach. Photo Dan Costa
Females and their pups in the water just offshore at Año Nuevo State Reserve. Photo: Dan Costa

Take the Self-Guided Mobile Tour

This piece is part of the Santa Cruz Marine Protected Areas Beaches Tour made possible by the Santa Cruz Collaborative with support from the California Marine Sanctuary Foundation and the Resources Legacy Fund. Download the free app with many tours of the Santa Cruz area and beyond.

takeTheTourbluetopoFontITC

Go to Mobile Ranger Guides in the Apple App Store
Go to Mobile Ranger Guides in the Google Play Store
  1. Sources



About The Author

Molly Lautamo is a content strategist and writer in Santa Cruz, California. She loves exploring and researching her surroundings and then writing about her discoveries to inspire others to get out and explore too. You can check out more of Molly's writing at mollylautamo.com.

Related posts

10 Comments

  1. Kathy Lutes

    Elephant seals are awesome!

    I can remember when the first elephant seals appeared at Piedras Blancas Big Sur – and now there is a huge colony just south of there.

    Reply

Leave a Reply

Your email address will not be published.