Elephant Seals

Why Are Elephant Seals Important?

Northern elephant seals (Mirounga angustirostris) are one of six pinniped species found in the San Francisco Bay Area. As top ocean predators, and prey for even larger predators like orca whales and great white sharks, they are a key component of the marine ecosystem. They spend most of their lives in the deep ocean waters of the North Pacific, journeying thousands of miles each year and diving to great depths in search of food. Changes in their populations often reflect changes in marine conditions, so monitoring them gives us important insights into the state of our oceans. Elephant seals can also be readily counted when they come ashore each year to give birth and breed (December-March), and later to molt (April-July). Point Reyes National Seashore is one of only about a dozen sites where northern elephant seals breed worldwide.

Map of northern elephant seal breeding sites
Above:  Map of northern elephant seal breeding sites. Click on the map to enlarge it and read more.

Why Do We Monitor Elephant Seals?

  • To detect long-term trends in elephant seal population size and reproductive success at Point Reyes
  • To determine long-term trends in elephant seal distribution on Point Reyes beaches
  • To identify existing or potential threats to the elephant seal population
  • To share and compare data with other northern elephant seal researchers

How Do We Monitor Elephant Seals?

Counts

NPS staff and trained volunteers conduct complete counts of elephant seals at each breeding site at least once per week throughout the elephant seal breeding season (December - mid-March). Counts are done for different genders and age groups (e.g. adult males, adult females, pups, yearlings, sub-adult males, etc...) with the help of binoculars and spotting scopes from established viewing locations on the cliffs overlooking the colonies. 

Tags

Each year, NPS staff affix pink numbered tags (seals born at other colonies receive different colored tags) to the hind flippers of 200-300 weaned pups to track their survival and dispersal in subsequent years. Staff may also apply temporary dye marks to some male elephant seals to track their movement among different beaches throughout the breeding season. Regular surveys are conducted to look for and record tagged seals on Point Reyes beaches. NPS tagging activities are authorized under National Marine Fisheries Service Permit No. 17152-00.

For more details on elephant seal monitoring at Point Reyes, check out the San Francisco Bay Area Network Pinniped Monitoring Protocol.

Photo of weaned elephant seal pupsAbove:  Weaned pups linger on the beach after their mothers have returned to the sea. During this time, NPS staff tag 200-300 of them so they can be identified when they are seen at Point Reyes or at other elephant seal colonies in subsequent years. Photo by Heather Jensen, NPS.

More photos can be viewed in the Elephant Seal Image Gallery.

Photo of Northern elephant seal bulls battle fiercely for access to females

Above:  Northern elephant seal bulls battle fiercely for access to females at Drakes Beach. Photo by Jane Khudyakov.

How Do We Use the Monitoring Data?


  • To ensure northern elephant seal and visitor safety through appropriate signage, staffing, visitor outreach, and beach closures
  • To document northern elephant seal colony expansion and interactions with other species.
  • To predict and prepare for the effects of climate change, such as sea level rise, on Point Reyes beaches and wildlife

What Have We Learned? 

Population

Once widely distributed along the California and Baja California coasts, northern elephant seals were hunted to the brink of extinction in the mid-1800s for their oil-rich blubber. Some researchers believe that as few as 100 seals may have remained before hunting was banned by the Mexican and United States governments in the early 20th century. The population has since been recovering, with added support from the U.S. Marine Mammal Protection Act of 1972 and they are recolonizing areas where they had been previously documented such as the Channel Islands and Point Reyes.

At Point Reyes, northern elephant seal colonies were absent for more than 150 years until a colony formed in the winter of 1981. The new colony grew exponentially until 1997-98. Growth continues at Point Reyes, though at a much slower pace. In 2012, preliminary results indicate that 723 pups were counted, a new high. Based on previous research establishing the typical ratio of pups to other elephant seal age groups, numbers of births can be multiplied by 3.5 to obtain a rough total population estimate. Using this calculation puts the Point Reyes population estimate for 2012 at more than 2,500 seals. Other research indicates that immigration is also contributing to population growth at Point Reyes.

Maximum Count of Northern Elephant Seal Pups, 2005-2012

Above:  The maximum number of northern elephant seal pups at Point Reyes is calculated as the sum of the maximum number of pups (live and dead) and weaned pups counted on a single census at each colony site. Data from 2010-2012 are preliminary and have not been analyzed.

The maximum counts were lower in 2010 because storms coinciding with extreme high tides resulted in many young pups being washed away, especially at Point Reyes Headlands sites. Overall, though, the number of pups born at Point Reyes continues to increase. 

Map of Point Reyes elephant seal breeding sitesAbove:  A map of the four main beach areas within Point Reyes where elephant seals congregate to pup, breed, and molt. A beach along Point Reyes Headlands was the first site to be colonized in 1981. As the population grew, seals began to use Drakes Beach, South Beach and beaches below the Chimney Rock Loop trail. Click on the circled beach areas to see a photo of each site.

Distribution

While Point Reyes Headlands pocket beaches were the most dominant breeding sites for a long time, more seals now give birth at Drakes Beach near the Chimney Rock parking lot. This is likely due to overcrowding and the fact that Point Reyes Headlands beaches face the open ocean and offer little protection from winter storms that can wash away and drown young pups. Females at Point Reyes Headlands sites may move to the more protected Drakes Beach when there is a stormy start to the pupping season. For example, during 1998 and 2010, turbulent El Niño years, more than half of the pups born at the Point Reyes Headlands were washed away, and several pregnant females moved to Drakes Beach to give birth.

Tagging

Surveys of tagged elephant seals at Point Reyes indicate that most of the seals coming ashore over the past several breeding seasons were originally born and tagged at Point Reyes. However, many elephant seals tagged at other colonies such as Año Nuevo, the Farallones, Piedras Blancas and the Channel Islands have also been recorded on Point Reyes beaches.

Disclaimer: The National Park Service shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data and related graphics are not legal documents and are not intended to be used as such. The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and consistent within the limitations of geospatial data in general and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data; it is not appropriate to use the related graphics as data. The National Park Service gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from an NPS server and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully on computer systems at the National Park Service, no warranty expressed or implied is made regarding the utility of the data on other systems for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. The National Park Service requests that the data user refrain from publishing these data and related graphics and wait until data is available in official, published reports.

Point Reyes Headlands (Main Colony) Drakes Beach Chimney Rock Loop South Beach

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