Shedding Light on Molting Harbor Seals in Marin

Molting harbor seals are counted from a distance using spotting scopes so as not to disturb these skittish creatures.

NPS

August 2018 - In June and July, harbor seals haul out every day to molt, which means they shed their fur and grow a new layer. Counting the resting seals gives park biologists important information about how harbor seal numbers might be changing over time.

During the 2018 molt season, a total count of 3,022 seals was recorded at eight Marin County monitoring sites. This is lower than the 18-year average of approximately 3,600 seals and is similar to the low count seen in 2017 (2,800).

Drakes Estero had the largest number of seals with almost 1,100, followed by Bolinas Lagoon with 650. Bolinas Lagoon has seen a large increase in seals since 2014, and has an 18-year average of 500 seals. Double Point—which for many years had been a top site with an 18-year average of 930 seals—continues the decline that started in 2015 with only 340 seals recorded during the 2018 molt season.

For more information check out the 2018 molt season monitoring update or contact Sarah Codde.