True Seals
Elephant Seals
Elephant seals are by far the largest of the different seals and sea lions found in Salish Sea. Adult males can be 15 feet long and weigh 5,000 pounds. These seals mate and give birth on beaches and islands off the coast of California and Mexico. Males make long distance migrations to southern Alaska and the Aleutian Islands and back twice a year while females tend to migrate west and have been sighted as far as Midway Atoll in the Northwest Hawaiian Islands. While they forage off the continental shelf where they make dives almost a mile deep, some elephant seals do come into the inland waters surrounding the San Juan Islands to haul out to rest. Elephant seals hold their breath for long periods of time even while resting on land. This regularly fools people into thinking they are dead. In the summer, large male elephant seals can be seen around the San Juan Islands, inspiring some and baffling others.
Thermoregulation in rehabilitating harbor seal (Phoca vitulina richardsi) pups: how core body temperature and surface temperature are associated with size metrics and the management practice of bathing
Vertical transmission of internal parasites in harbor seal (Phoca vitulina richardsi) pups in San Juan County, Washington
Seals on the Run
Every summer, dozens of stranded baby harbor seals are brought to centers where they’re rehabilitated and released back into the wild. People expect these animals will behave like wild seals. But do they?
To find out, SeaDoc and colleagues satellite-tagged and tracked 20 harbor seal pups – half rehabilitated, half naturally weaned. The differences were big. Rehabilitated seal pups took off like torpedoes after release, traveling three times farther daily and dispersing three times as widely as the wild ones. And the rehabbed pups only transmitted signals for half as long as their wild cohorts, which could relate to how long they survived.
What’s extra fascinating here is that we’re talking about a mammal that spends just a single month nursing before it’s left on its own to survive. But if human-reared pups are traveling so much further, it could mean that wild pups actually learn quite a bit about foraging in the short time they spend flippering alongside their mothers, even if they’re only nursing and not catching fish. It could also mean that wild pups “imprint” on a local area during their first month. Or it might mean that rehabbed pups are naive to navigating the strong currents that sweep through the San Juans. It is time to learn how best to enhance rehabilitation techniques to get pups behaving more like wild seal pups after release.
More Information:
SeaDoc's paper was written by Joe Gaydos and Ignacio Vilchis of the SeaDoc Society (UC Davis), Monique Lance and Steven Jeffries of the Washington Dept. of Fish and Wildlife, Austen Thomas of the University of British Columbia, Vanessa Greenwood and Penny Harner of Wolf Hollow Rehabilitation Center, and Michael Ziccardi of the Wildlife Health Center at UC Davis.
The abstract is here. If you would like a copy of the full manuscript please email your request to seadoc@seadocsociety.org.
This study was funded by NOAA's John H. Prescott Marine Mammal Rescue Assistance Grant Program and private donations from SeaDoc supporters, including a significant donation from Bill and Lannie Hoglund. For this particular study, the private donations were a critical part of the mix because the Prescott funds could not be used to study wild-weaned seals.
Overview of post-rehabilitation research:
At the 2012 North American Veterinary Conference, Joe Gaydos gave an overview of the need for post-rehabilitation studies and reviewed the studies performed to date. He also discussed the role of veterinarians in marine mammal rehabilitation. Read the PDF.
Stranded seal recovery:
Stranded seals are generally found in the summer months. There are a number of reasons why pups become separated from their mothers, including illness, interference from dogs and humans, and maternal death. SeaDoc's summer interns assist with the Marine Mammal Stranding Network in the San Juan Islands. They often provide first-line veterinary response when pups are picked up and transported to the rehab center.
Wild seal capture:
The wild-weaned seals were captured by the investigation team from a haulout location in the San Juan Islands.
Keep your distance from marine mammals:
We always like to remind people that Federal law requires everyone to stay at least 100 meters away from marine mammals like Harbor Seals. Do not approach pups you think are stranded or abandoned. They may be just waiting for their mother to return, but if you approach you may scare off the mother and cause the pup to be abandoned.
Harbor Seal facts:
Did you know the milk of harbor seals is 40% fat? Or that they can dive up to 600 feet? View more harbor seal facts.
Harbor Seal skeleton available for display:
SeaDoc has a mounted skeleton of a large male harbor seal found dead on a beach in San Juan County. The skeleton travels to schools, banks, and other public display locations to help people learn about Salish Sea marine mammals. If you're interested in displaying the skeleton at your place of business, get in touch. See pictures.
Surprise your friends with a Harbor Seal ringtone:
Just for fun, we took a recording of a squawking young seal and turned it into a ringtone for the iPhone. It sounds a little bit like a badly out-of-sorts child, and definitely gets some strange looks in the grocery store. Details.
Postrelease movement of rehabilitated harbor seal (Phoca vitulina richardii) pups compared with cohort-matched wild seal pups
Mortality related to Spotted Ratfish (Hydrolagus colliei) in Pacific harbor seals (Phoca vitulina) in Washington State
Harbor seal diet in northern Puget Sound: implications for the recovery of depressed fish stocks
Press Release: Rockfish are not a major prey item for seals
September 28, 2012
Contacts:
Dr. Joe Gaydos, SeaDoc: 360.914.1083
Monique Lance, WDFW: 253.691.3409
Dr. Alejandro Acevedo-Gutiérrez, WWU: 360.650.4590
Harbor seals primarily eat salmon and schooling forage fish.
A study published last week in the journal Marine Ecology Progress Series indicates that robust local seal populations consume a diverse menu of fishes and invertebrates and that depressed rockfish species are not a major part of their diet.
The Salish Sea has a very robust harbor seal population that has been at or near carrying capacity for nearly two decades. This has made fishers and scientists wonder what impact these top-level predators could be having on the recovery of depressed fish populations. Approximately 15% of the fish species in the region are listed as threatened, endangered, or are candidates for listing. A multi-year study funded by the SeaDoc Society (a marine science program of the UC Davis School of Veterinary Medicine), the National Science Foundation and the Washington Department of Fish and Wildlife provides insight into this complex question.
According to Monique Lance, a wildlife research biologist at the Washington Department of Fish and Wildlife and the lead author of the study, “harbor seal diet is quite diverse, not only in the species they eat, but also in the variability we see depending on the season, year and location.” Harbor seals consumed over 45 species of fishes as well as invertebrate species like squid, octopus and shrimp. While individual seals likely have different dietary preferences, as a group, seals feed on fish that are seasonally and locally abundant. They eat more salmon in the summer and fall (especially pink salmon when they are running), herring year-round, and sand lance, anchovy and juvenile walleye pollock during the winter and spring.
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Additional Info
Download a PDF of the press release.
Link to the citation/publication.
You may also contact us at seadoc@seadocsociety.org to request a copy of the publication.
Images for press use:
Photo by J. Gaydos. Hi-res version (4.5MB).
Quillback rockfish by Janna Nichols. (No hi-res available)
Harbor seal eating salmon while gull watches by J. Gaydos. Hi-res version (1.2MB)
