Tag! Fur seals are it on the Farallones

September 23, 2019

Historically, fur seals were the most numerous pinniped (seals and sea lions) found on the Farallon Islands National Wildlife Refuge. However, after decades of fur trading the population was locally extirpated by around 1834. Fur seals were absent from the Farallones for over 100 years, until a few individuals began visiting the islands to haul out during the 1970’s. It took another two decades before the first pup was observed in 1996 after recolonization by breeding adult animals (see here for more on the history of the Farallon rookery).

Northern fur seals on West End, Farallon Islands National Wildlife Refuge

Since that first pup was born the Farallon rookery has grown exponentially and today there are approximately 2,000 pups born a year on a remote wilderness area of the island called Indian Head Beach. Now that the rookery is re-established and growing rapidly, we decided it was time to learn more about our fur seals and to determine what happens to the pups that are born on the Farallones. To do this, Point Blue partnered with NOAA’s Marine Mammal Lab (MML) out of Seattle, WA to begin tagging pups. The goal is to mark pups with individually numbered flipper tags and then resight these individuals again in future years (much like Point Blue has been doing with seabirds and elephant seals for the past 50 years). Researchers from the MML have been doing similar work for decades on San Miguel Island in southern California and many tagged individuals from that rookery have been sighted at the Farallon Islands.

Northern fur seal 937A, originally tagged at San Miguel that has moved north to join the Farallon rookery

For the past three years Point Blue Farallon biologists Pete Warzybok and Jim Tietz have worked with Tony Orr (MML) and Ryan Berger (formerly Point Blue, now with The Marine Mammal Center) to deploy tags on fur seal pups at the Farallones. Hopefully, these tagging and resighting efforts will allow us to learn more about pup survival at this colony, recruitment of young into the future breeding population, and movement of individuals between colonies. The project has already proven successful as this season’s efforts have resulted in the sighting of 3 tagged individuals from the first tagging efforts in 2017.

Farallon fur seal, tagged 42F in September 2017, returned to the rookery in 2019

This year, Pete, Jim, Tony, and Ryan, were joined by Point Blue research assistants Amanda, Joey, Kurt, John, and Melissa for two days of intense and exciting field work with these incredible and resilient animals. We were able to put out tags on 101 pups, bringing our three year total to 265. This project has been an excellent example of how Point Blue can accomplish more through strong, collaborative, partnerships. Over the next several years, we hope that many more of our tagged pups will be resighted (either on the Farallones or at other rookeries) and to continue to work with the MML and TMMC to improve our understanding of the local population dynamics of fur seals breeding in the California Current System.