Updated: May 6
With winter coming around the corner, behemoths over ten feet long gather offshore in Central to Southern California. These marine titans are known as the northern elephant seals, Mirounga angustirostris. Their winter gathering in Southern California is actually part of a biannual migration, which is identified as one of the longest routes among mammal migrations globally (NOAA).
Northern elephant seals are pinnipeds and members of the “true seal” family. Being a true seal means they have ear holes, have more blubber, use their rear flippers to swim, and cannot walk. They are the family’s largest members in the Northern Hemisphere. Females range from 600-900 kg (1,323 lbs to 1,984 lbs) while males can weigh up to 2300 kg. Along with the size difference, males will have prominent trunk-like noses, which contrasts with the females’ smaller noses (Animal Diversity Web).
The adult northern elephant seals participate in biannual migration, which contributes to foraging, breeding, or other physiological needs. The two migrations total up to 250-300 days annually spent at sea and a 13,000 mile round trip along the Pacific coastline. The primary destinations for the biannual migration depend on the seals’ needs during that time.
Before migrating in the new year, from December to March, elephant seals breed off the Channel Islands, California coast or Baja California, Mexico (National Park Service). Another name for these breeding sites are rookeries. Elephant seals are polygynous, which means the male will mate with multiple females and form a group called a harem (Nature Education). Usually the strongest male will mate with females on the rookeries and dominance is determined by fighting (National Park Service). After the dominant male is established and mates with the female, the latter will return to the same site after about 291 days to give birth to a pup.
Once the breeding season wraps up, the elephant seals migrate northward to feed in Alaska or the Aleutian Island region. Though elephant seals gather near Alaska/Aleutian Islands, the males and females feed in specific spots. Females feed in the open ocean around Washington and Oregon while males feed along the Aleutian Islands and Gulf of Alaska coastlines. Their diet includes cephalopods (squid and octopus) and crustaceans (shrimp and crab), but they can eat rays and sharks as well (National Park Service). Additionally, elephant seals will dive down and stay submerged to get their food. When they dive, an elephant seal can hold their breath for up to half an hour or more. During that time, they can dive as far down as 5,141 ft (Marine Science).
Finally, they will temporarily leave their feeding sites to spend April to August molting. During this process, they not only lose their fur; they will also shed the top layer of their skin (National Park Service). Molting has beneficial effects on the northern elephant seals. It helps redirect blood flow to the surface and keep vital organs warm because they spend time out in freezing ocean conditions, ranging from 3 to 13 ℃ (Canadian Journal of Zoology).
During their migration route and stops, northern elephant seals can encounter anthropogenic, human-caused, threats. Prominent ones include fishing gear entanglement and vessel strikes. However, there are local conservation efforts to rescue injured animals or educate the public about this species. In Laguna Beach, California, the Pacific Marine Mammal Center rehabilitates pinnipeds (including elephant seals) back to health before releasing them back into the wild. This organization was developed 6 years prior to the Marine Mammal Protection Act and has rescued a total of 10,000 animals over the past few decades (OC Register). Moreover, their website provides a series of instructions on how to approach and report stranded seals.
People can help out as well by donating or volunteering to local conservation/rehabilitation groups that support the protection of these and other marine mammals. Also, people can report to the Pacific Marine Mammal Center (949) 494-3050, Animal Control (949) 497-3552, or Marine Mammal Care Center (310)-548-5677 if they spot a stranded, injured, or harassed seal out on the Orange County beaches.