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Seals and sea lions guard human health

Can it be that those verbally scorned, physically assaulted, and considered by some to be vermin, ironically, be allies to the very ones who condemn them?

One sign of health is the ability to reproduce, have the young survive to adulthood, and and have adults thrive. Here, California harbor seal (Phoca vitulina) adults and pups let us know that there is hope for our ocean’s future. ©2011 Judith Lea GarfieldI refer you to Exhibit A, our local seal and sea lion populations. Plenty of data show that while these kindred mammal spirits toil away at their own survival, they simultaneously act as sentries to guard the health of the ocean and humans. Personally, I can’t think of any vermin providing an equivalent and planetwide environmental service.

This is why NOAA (National Oceanic and Atmospheric Administration), with offices on the hill above Scripps Institution of Oceanography, brought into its fold the Human Health Initiative, which addresses the importance of marine organisms as sentinels because they portend health-threatening trends and impacts for us. While the designated sentinels include all marine mammals, no coastline is blessed with every such species. What luck we have our own personal barometer pinniped populations nearby. Both harbor seals (Phoca vitulina) and California sea lions (Zalophus californianus) make up only small populations, but however many numbers we have are better than no pinnipeds at all, particularly now that their job description has extended to helping us gauge the unknown potential short- and long-term consequences of global climate change.

Because marine mammals like California sea lions (Zalophus californianus) are conspicuous and likely to be observed by nonscientists, health maladies that impact these species may make humans more likely to pay attention to deteriorating ocean health issues. ©2011 Judith Lea GarfieldAccording to various scientific journal articles (e.g., Veterinary Pathology, May 2011; Oceanography, June 2006), most marine mammals (like us) have long life spans, are long-term coastal residents, feed on prey we also eat and carry large fat stores (typically where manmade toxins collect and bide their time before oft-unknown triggers set disease in motion). Consequently, marine mammals are our doppelganger representatives in the ocean ecosystem; they interact in the three-quarters of Earth’s real estate that we are not in the same way privy. 

Environmental degradation from human activities (like pollution, overfishing and climate change) is showing up as new diseases in ocean plants and animals, with potential for those diseases to be passed to us directly or eventually. As an example, a percentage of stranded California sea lions are showing up with an alarmingly high incidence of a newly described urogenital cancer. The disease appears to be rooted in a combination of novel herpes virus and PCB and DDT exposures (human-created contaminants swirling in the waters of their — our — feeding grounds).

California sea lions. © Judith Lea GarfieldAnother shared human and marine mammal disease, sometimes fatal to both, is a parasite that causes toxoplasmosis. It has reared its infective head at more than half of southern sea otters (Enhydra lutris nereis) found beached. And we can’t ignore those pesky algal bloom species that carry a little something extra — deadly toxins. The algal laundry list of biopoisons includes those species responsible for neurotoxic, diarrhetic and paralytic shellfish poisonings, now permeating all coastlines where they have been incriminated in mass mortalities of dolphins, sea lions and manatees. So you can see how our desire for many of the same food preferences as animals the most like us — without being us — can result in our being afflicted by similar diseases.

Maybe it’s time to trade in those rose-colored glasses and get a new prescription. It seems shortsighted to scapegoat the local pinniped population with a litany of unsubstantiated fears. According to the Marine Mammal Commission (2004), virtually all threats to marine mammals are ultimately related to humans via our population size, growth rate, and consumption and behavior patterns. We need our pinnipeds, if for no other reason than purely selfish human survival. The San Diego Lifeguard Service likes to tout itself as a 24/7 service, but it’s really our local pinnipeds who trump them as the true lifeguards at the beach. I am bewildered why everyone isn’t enamored of these charismatic animals and our great fortune in having them as part of our urban landscape. It’s a wonder they are here considering all the depressing news about the environment.

That our pinniped populations do exist here should give us hope for the ocean’s health and inspire us, both as individuals and as a community, to do much more to secure the natural world for future generations. Yes, we need the will, but it is possible. Maybe those folks with exaggerated, negative views of our local pinnipeds will change their minds once they discover the benefits to themselves. Choosing to shift from a passion for pinniped eradication to pinniped support will also free up time and energy to devote to other inclusive community quality-of-life issues, such as raising funds to extend the hours of La Jolla’s Rifford Library. Wouldn’t that be a thrill? And what better time to hope than this holiday season?

— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to