Overview

Northern elephant seals (Mirounga angustirostris) are the largest pinniped and “true” seal species found in Washington. While they spend most of their lives at sea, they must come ashore to breed and molt their fur. These expert divers can reach depths of nearly a mile (1600 meters) and hold their breath for almost two hours. They have one of the longest migrations of any mammal (Stewart and Hubert 1993).  

Elephant seals at a glance

• Mass: 590-2,000 kg (1,300 - 4,400 pounds)
• Length: 3-4 meters (10-13 feet)
• Lifespan: 13-19 years
• Eats: squid, schooling fish, sharks, rays
• Natural predators: Bigg’s orcas, sharks      
• Threats: entanglement, vessel strike

Status, trends, & events

Historically harvested for their oily blubber, northern elephant seals were hunted heavily in the 19th century and were believed to be extinct by 1892 (Townsend 1912, Hanna 1925, Stewart et al. 1994). A small remnant population of ~50-100 animals remained off the western coast of Mexico. After gaining protection in 1922, their population steadily grew (Bartholomew and Hubbs 1960, Cooper and Stewart 1983) from these few animals to more robust populations in the U.S. and Mexico of approximately a minimum of 220,000 individuals as of 2010 . Since 1988, the population is reported to have grown annually at 3.1%. However, due to the intensive hunting in the 19th century, the resulting population bottleneck left future generations of seals with a loss of genetic diversity and fitness (Hoelzel et al. 2002).

Sightings of elephant seals were once considered rare in the Salish Sea, but increasingly single individuals are known to haul out onto sandy beaches on Smith, Protection, and Whidbey Islands. Race Rocks, an ecological reserve southwest of Victoria, British Columbia, Canada, is believed to be the most northerly breeding colony on the Pacific coast (Cowan and Carl 1945). In 2019, three pups were born at the reserve (Race Rocks Ecological Reserve). Tagged individuals from California colony sites such as Ano Nuevo Island have been tracked along the outer coast and within inland waters of Washington State, with some even reaching south as southern Puget Sound.

Starting in 2010, a local breeding population established itself along the lower west side of Whidbey Island in Puget Sound, and are known locally the Mutiny Bay group, after the body of water that became the focal point of the group’s origins (Orca Network/Central Puget Sound Marine Mammal Stranding Network, unpub data). In the spring of 2010, an adult female (named “Ellie” by locals) appeared on the beach at Mutiny Bay where she has returned every year to molt (2010-2023). In 2015, Ellie returned in March to the same beach and gave birth to a male pup (now known as “Ellison”). Ellison established Baby Island as his territory in 2015, and returns to this spit along the east side of Whidbey Island every year to molt (2016-2023). During winter and spring 2023, Ellison was observed to display what is assumed to be sexual aggression toward more than 12-15 adult female harbor seals on the east side of Whidbey Island (Orca Network/Central Puget Sound Marine Mammal Stranding Network, unpub data). Sexual aggression towards younger northern elephant seals and other seal species has been observed in Puget Sound and in other parts of their west coast range (Le Boeuf and Mesnick 1991, Rose et al. 1991, Hayward 2003).

Numerous reports have been received, along with physical evidence of injuries, that this male has made attempts to mate with adult harbor seals, resulting in multiple deaths for the harbor seals (2023). In March 2018, Ellie gave birth to a female pup (“Elsie Mae”) at the Mutiny Bay beach which was tagged with a rear flipper roto-type of tag. Elsie Mae makes yearly sojourns during the same general time frame (March - April) to the city of Anacortes in northern Puget Sound to molt (2020-2023). In March 2020, Ellie gave birth to a third pup at Mutiny Bay beach, a female (“Eloise”) that suffered extensive hind flipper damage from a coyote attack. This female pup was last sighted in January 2021, on Whidbey Island. In March 2021, Ellie gave birth to a male pup, again at Mutiny Bay beach, which was last sighted in May 2021, near Port Ludlow, a town across Puget Sound from the western side of Whidbey Island. Ellie’s pup, Elsie Mae, gave birth to a male pup in northern Puget Sound in January 2022, which has been molting yearly since 2022 in the town of Victoria, southern Vancouver Island, Canada.

Natural History

Distribution and occurrence

Northern elephant seals spend the majority of their time at sea, coming ashore for just a few weeks each year (LeBoeuf and Laws 1994). Elephant seals undergo the process of a catastrophic molt, meaning they lose all of their fur and upper layer of skin at once. During this molting phase, they are unable to enter the water and therefore do not eat. Elephant seals typically molt between April and August. 

Northern elephant seals are distributed in the central and eastern North Pacific Ocean, from as far north as Alaska down to southern Baja California in Mexico (Lowry et al. 2014). They usually breed and give birth in the Channel Islands off California or Baja California in Mexico, as well as at Piedras Blancas in central California and Pt. Reyes in northern California, from December to March, primarily on coastal islands. Males feed near the eastern Aleutian Islands and in the Gulf of Alaska, and females feed farther south, in the offshore waters of Washington and Oregon. Adult elephant seals return to beaches to molt between March and August. Females return earlier than females. Within Puget Sound, they are often spotted at haul outs on Protection, Smith, and Minor Islands and more recently on Whidbey and Fidalgo Islands (Jeffries et al. 2000) often in the company of other pinnipeds such as harbor seals (Phoca vitulina). In Washington inland waters, solitary animals are typically observed, except for mother and pup pairs.

What eats them?

As in California and Mexico, the most frequent natural predators of northern elephant seals while in Puget Sound are Bigg’s, or mammal-eating killer whales (Orcinus orca) — also referred to as West Coast Transients and sharks (Ainley et al. 1981, Le Boeuf et al. 1982). Pups and juveniles may be exposed to terrestrial predators such as coyotes (Norman, pers observation).

What do they eat?

Adults return to their feeding areas again between the spring/summer molt and the winter breeding season. Elephant seals feed on squid and bony fish as well as sharks and rays during long deep foraging trips that can average from 26-36 minutes, and up to 109 minutes (Antonelis et al. 1994, Robinson et al. 2012, Keats et al. 2022). However, evidence of feeding within Puget Sound waters has not yet been witnessed. It is presumed that because many of the observed elephant seals are molting, they would not be foraging anyway.

Biology

Northern elephant seal pups are born black, or dark gray, until they are weaned at about 6 weeks of age. They then molt and turn light silver in color. Males reach puberty at approximately 7 years old, at which time they develop a large inflatable nose, or "proboscis." The proboscis overhangs their lower lip by about 8 inches and is the source of the species’ name, elephant seal, due to its similarity to an elephant’s trunk. Males also develop a robust, thick neck with calloused skin that appears pink and light gray. This thickened skin creates a shield to protect them from harm when fighting other males. In contrast, females maintain their smooth necks and smaller noses.

Fully grown adult males may reach lengths of greater than 4 meters (13 feet) and weigh almost 2,000 kilograms (4,400 pounds). Females are significantly smaller than males but can grow to approximately 3 meters (10 feet) and weigh up to 590 kg (1,300 pounds). Adults are dark brown or gray.

Northern elephant seals spend about 9 months of the year foraging far offshore in pelagic waters (Le Boeuf et al. 2000). For a majority of this time, the seal is active underwater, diving to depths of approximately 300-750 meters (1,000 to 2,500 feet) for 20-30-minute intervals interspersed with only short breaks, of approximately 1-2 minutes, at the surface; therefore, they are rarely sighted out at sea. Recent studies have even shown they can even drift off to sleep while diving underwater and sleep for less than two hours per day (Kendall-Bar et al. 2023). When on land, they tend to prefer sandy beaches. During the mating season, northern elephant seals will fast, resulting in a loss of up to 36 percent of their body weight. Through the molting period (4-5 weeks), elephant seals shed their short, dense fur in addition to large patches of old skin (Worthy et al. 1992).

Breeding takes place from December to March, with gestation lasting approximately 11 months. Northern elephant seals are polygynous breeders with formation of a social hierarchy (LeBoeuf and Laws 1994). Bulls will form harems when they are 9-10 years of age and will battle other males. The adult males use their large, inflatable proboscis during the breeding season to produce sounds when vocally threatening other males. Female elephant seals come ashore and give birth to a single pup that was conceived the previous breeding season (Huber 1987). Pups are typically born in early winter (December to January); however, in Washington State, they are born in early spring (March) (Norman, pers observation). The reason for this is unknown but may be due to the colder and harsher winter climate at higher latitudes in Washington compared to Oregon and California (Hodder et al. 1998). Pups nurse for about a month, at which time they will wean (Le Boeuf et al. 1972). Just before leaving her pup, the mother will breed again and then return to the sea. Females generally have a longer life span (~19 years) than males (~13 years). It is unknown why the Mutiny Bay group in Washington pups during late March compared to the remainder of the northern elephant seal population which pups during December and January. Perhaps the later pupping schedule in Washington may serve as an adaptive mechanism to cope with a changing environment or provide a greater chance for pup survival in a more northerly climate.

Other threats to northern elephant seals, in addition to natural predators, include low genetic diversity, entanglement in fishing gear, and inadvertent vessel strikes, climate change, and disease (Kovacs et al. 2012). The projected increase in vessel traffic resulting from declining Arctic Sea ice may increase the probability of vessel strikes and exposure to ship noise. Serious injuries and deaths have also been reported in California and Oregon due to shootings, marine debris entanglement (other than fishery), dog attacks, harassment, and vehicle collisions.

Northern elephant seals may be affected with a skin condition of unknown cause called northern elephant seal skin disease (NESSD) (Beckmen et al. 1997). Skin lesions are characterized by patchy to extensive hair loss and hyperpigmentation, skin surface ulceration, and occasionally, massive skin necrosis. Affected animals tend to be younger (<3-4 years of age) and are often emaciated, dehydrated, and depressed. If they contract a blood infection (septicemia), mortality may increase significantly as the severity of skin ulceration increases. In studies of NESSD, affected seals have exhibited decreased levels of blood thyroid hormone, serum iron, calcium, albumin, and cholesterol, but increased levels of organic pollutants such as PCBs (Yochem et al. 2008). However, the cause of this skin disease syndrome remains unknown.

Data sources & gaps

Monitoring and information gaps for this species in Puget Sound are numerous. Currently there are no regular monitoring efforts to estimate population numbers or examine trends in Puget Sound. Increased and more consistent monitoring efforts could help to determine exactly how northern elephant seals use these waters, and their impacts on other species (including on threatened fish stocks). The source colony (California or Oregon) of the Mutiny Bay local population is unknown.

Methods & statistics

The population time series graph was constructed from data on annual pup counts, surveys, and estimates of human-caused mortality. The distribution map was compiled from all available data sources (subset listed in References section).

Links

Parnell, Laas. (January 25, 2019). Elephant Seal Pups.  Retrieved from blog: http://www.racerocks.ca/tag/elephant-seal-pup/

Orca Network (March 11, 2022). Baby Name Announcement: https://www.facebook.com/OrcaNetwork/posts/baby-name-announcementthe-elephant-seal-pup-born-january-31st-to-elsie-mae-has-b/258193856523796/

Orca Network (November 28, 2021). The Story of Elwood, the elephant seal pup: https://www.youtube.com/watch?v=-xvpgpU1rn0

King5 News (April 29, 2021). Young elephant seal rescued from storm drain on Whidbey Island: https://www.king5.com/article/life/animals/young-elephant-seal-rescued-from-storm-drain-on-whidbey-island/281-9613c6be-c552-4720-8a63-12a9c30e78cb

Orca Network. Whidbey Island-born elephant seal family newsletters: https://indigo-ukulele-jm29.squarespace.com/mmsn-newsletters#elephant-seals

References

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Bartholomew G, Hubbs C. 1960. Population growth and seasonal movements of the northern elephant seal, Mirounga angustirostris. Mammalia. 24:313-324.

Beckmen KB, Lowenstine LJ, Newman J, Hill J, Hanni K, Gerber L. 1997. Clinical and pathological characterization of northern elephant seal skin disease. Journal of Wildlife Diseases 33(3):438-449.

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Acknowledgments

Funding for this article was provided by the University of Washington Puget Sound Institute with support from the U.S. Environmental Protection Agency and the Puget Sound Ecosystem Monitoring Program. Photos were generously provided by the cited contributors.

Licensing & attribution

Data and products from the PSEMP Marine Mammal Work Group are governed by a Creative Commons BY-NC-SA license. Attribution should be to: “PSEMP Marine Mammal Work Group” with the link: https://psemp.net/mmwg.