Point Reyes Elephant Seal Counts Hit New Highs in Winter 2021-2022 Despite a Tsunami

Northern elephant seals at Point Reyes National Seashore reached new highs in winter 2021-2022. The peak counts of all seals, of cows and of pups each reached a new high, even though a tsunami and two king-tide events struck during pupping. The National Park Service's season summary pulls together the numbers and a run of weekly field notes.

Image from the National Park Service: weaned pups gather in groups for temperature control, safety and company. NPS / Marjorie Cox, NMFS Permit No. 21425.

The season in numbers

• The breeding population grew again, continuing the trend at the Point Reyes colony.
• The highest count of weaned pups was 1,126, out of 1,294 pups born.
• Researchers flipper-tagged more than 500 weaned pups.
• The first pup of the season was counted on December 25. From January 13, total and female counts ran above the 2005-2021 average at the three park colonies, driven by Drakes Beach.

Image from the National Park Service: the peak total, cow and pup counts all reached new highs in 2022.

A beach that took off

Seals are moving between the park's sub-sites as numbers grow, and Drakes Beach has changed most. Researchers split it into DB1, the beach under the Elephant Seal Overlook, and DB2, the much longer stretch to the Kenneth Patrick Visitor Center. DB2 now holds over 500 breeding females at the peak of the 2022 season, while DB1 is declining, probably because seals are shifting to DB2.

Image from the National Park Service: peak breeding females on Drakes Beach.

Seals can also turn up in front of the visitor center. In 2021 and 2019, winter storms led females to give birth right there. This season, pregnant females were deterred from giving birth in front of the building, so no harem formed, though weaned pups still moved in.

Surviving a tsunami

A tsunami one weekend closed the park's beaches to people, but the colony had to stay put. Beaches with many seals were repeatedly flooded by surges that matched the morning high tide. Researchers saw some pup loss but no dramatic drop. Pups cannot swim, and one swept out could drown or lose its mother, so experienced mothers use their bodies to block pups from the water's edge. King tides over seven feet later did not appear to disturb the colony or cost many pups.

Tags and what they tell

Researchers tag weaned pups to follow their movements within the park and to other colonies. A tag put on at weaning also reveals the seal's age for as long as it stays on. The light tags go in the webbing of the hind flipper, and each colony has its own color: pink for Point Reyes and the Farallon Islands, green for Año Nuevo and white for San Simeon.

Image from the National Park Service: researchers tag a sleeping weaned pup. NPS / Marjorie Cox, NMFS Permit No. 21425.

Image from the National Park Service: a pink Point Reyes tag. NPS / Marjorie Cox, NMFS Permit No. 21425.

Tags also reveal characters. A bull marked with the dye letters D3 was tagged as a pup at Drakes Beach in 2011 and, at 11, held alpha status again after doing so in 2020 and 2021. Only about 5 percent of males born survive to adulthood and only about 1 percent mate successfully. A pregnant female nicknamed Shark Lady, tagged as a pup at Año Nuevo in 2005, carries a large healed shark wound and has been seen at Point Reyes since 2013, pregnant or with a pup. Staff also saw a pregnant female on Drakes Beach who had been tagged as a pup at the Historic Lifeboat Station and gave birth there in 2021.

Northern elephant seal facts from the weekly notes

Pups weigh 60-75 lbs at birth and about 300 lbs weaned, nursing for roughly 28 days. Seals dive about 1,000 feet on average; the deepest recorded dive, by an adult female, was 5,788 feet. At sea they spend about 90 percent of their time underwater, surfacing for around two minutes between dives.

Life on the beach

• Timing. A UC Santa Cruz study that tracked females by satellite found they gave birth on average 5.5 days after arriving on land.
• No water to drink. Seals fast on land for about three months (males), one month (females) and two to three months (weaned pups) and do not drink. They conserve water through bony structures in the nose that condense moisture from exhaled air, and through long breath holds; an adult may not breathe for over 20 minutes. A male can lose up to 40 percent of his weight, about 2,000 lbs, over the season.
• Hot days. Seals shed heat through their flippers, flip sand onto their bodies to cool by evaporation, and in the calm waters of Drakes Bay some females take their pups into the water to cool off.
• Voices. Males use "clap threats" that carry a personal signature, and lower-ranking males use them to decide whether a fight is worth the energy; they can recall a rival's signature from earlier years. Pups squawk to call their mothers, and a UC Santa Cruz study found females can recognize their own pup's calls, though some are more consistent than others.
• A rare catch. Researchers watched a juvenile seal come ashore carrying a spotted ratfish and eat it, an extremely rare sight. It may have been a one-off, or young seals may forage closer to shore than adults; juvenile foraging is far less studied than adult foraging.
• Delayed pregnancy. Seals use delayed implantation: the fertilized egg floats in the uterus for about 3.5 months, so birth can fall at the right time whenever mating occurred. Total gestation is about 11 months.
• Weaning. Pups get no care after weaning at about four weeks. They gather in pods, mock-fight, and over two to three months on the beach and in shallows learn to swim and dive. In a UC Santa Cruz study, one weaned pup dived 90 feet on her first dive from the colony and over 700 feet after three days at sea.

Visiting

Most breeding seals have left by spring, but weaned pups stay on the beaches through April and some males into late March. Seals can be seen from the Elephant Seal Overlook and on the beach in front of the Kenneth Patrick Visitor Center. They are at Point Reyes year-round: adult females and juveniles return to molt from March to June, adult males molt from June to August, and young seals haul out in the fall. Visitors should keep their distance for their own safety and to avoid disturbing resting seals.

Sources

• National Park Service, Point Reyes National Seashore, Elephant Seal Monitoring Season Summary: Winter 2021-2022; rewritten in hubnx's own words.