Marin County's Harbor Seals in 2022: Record-Low Counts and Coyotes

Seals under pressure

Harbor seals live double lives — half on land, half at sea — so they must dodge predators in both. In recent years the seals of Marin County, California, have faced more coyotes, and in 2022 the problem continued.

National Park Service staff and volunteers in the Harbor Seal Monitoring Program count seals in spring, during the breeding season, and in summer, during the molt, when seals spend long stretches ashore shedding and regrowing their fur.

Where coyotes have come

• Double Point: coyotes became regular about five years earlier — just as fewer seals began hauling out there.
• Drakes Estero: multiple coyotes appeared regularly in 2021, and seal numbers dropped dramatically.
• 2022: numbers stayed low at both Drakes Estero and Double Point.
• Bolinas Lagoon: a coyote was seen at the colony — the first in many years — at the end of the molt season, and it killed a seal.

Breeding season

Monitors counted 876 pups, one of the lowest counts on record. Pup numbers normally cycle high and low, and long-term reproductive success is fairly stable; the next few years will show whether numbers rebound. Every site was below average except Bolinas Lagoon (above average for several years) and Point Bonita in the Marin Headlands, a small pupping site.

Maximum harbor seal counts by site, 2022: breeding season (adults and pups) and molt season (all seals). NPS.

Maximum pup counts at Marin County sites, 2000–2022. The solid line is the 2000–2021 mean (1,069); dashed lines mark one standard deviation. Not all sites were surveyed in 2020. NPS.

Molting season

Monitors counted 2,149 seals — far below the long-term average of 3,490 and the lowest ever recorded by the program, continuing a long decline.

• Drakes Estero and Double Point were each more than 50% below their long-term averages.
• Bolinas Lagoon was the only site above average, and has become a very important site for Marin's seals — which makes the coyote there worrying. Next year will show whether coyotes become regular at Bolinas and change how seals use it.

Maximum molt-season counts at Marin County sites, 2000–2022. The solid line is the 2000–2021 mean (3,490). NPS.

Weekly maximum counts by site and survey week, 2022. NPS.

Thanks: Marin County Parks natural resources staff helped monitor Bolinas Lagoon in 2022, a collaboration the park hopes will become permanent.

More: the San Francisco Bay Area Network's pinniped monitoring and the Pacific Coast Science and Learning Center's harbor seals pages.

Sources

Based on "2022 Harbor Seal Monitoring Updates," San Francisco Bay Area Network, National Park Service (Point Reyes National Seashore and Golden Gate National Recreation Area); a work of the United States government in the public domain. The NPS notes that its data and graphics are not legal documents and should be obtained directly from NPS sources for any use as data. The article's photograph of a coyote among the seals, credited to an individual volunteer, is left out.