Zalophus Invade the Farallones
October 13, 2015
Before the early 1800’s the Farallon Islands were home to hundreds of thousands of Northern Fur Seals (Callorhinus ursinus). The Northern Fur Seal’s coat boasts an impressive 9,000 hairs per square inch. Their precious pelts attracted Russian and Bostonian fur traders, who ruthlessly hunted them until none were left on the islands. Little is known about the population sizes of other species of pinnipeds (seals and sea-lions) during that time. But after Northern Fur Seals were extirpated from the Farallones, the California Sea-Lion, AKA Zalophus californianus, has likely been the most abundant pinniped on the island.
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| The relatively thin fur of Zalophus coats were not as sought after as Northern Fur Seal coats. |
Over the last several years during pinniped censuses we typically count approximately 3-4 thousand Zalophus between August and November. When the Point Blue Fall crew arrived on the Farallones this August, we found that the number of Zalophus using the island was over 8 thousand!
This huge increase has caused the Sea-Lions to push further up onto the island than usual. Most of the Marine Terrace, where we normally walk transects looking for migrant landbirds and shorebirds, is now occupied by about 5,000 barking Sea-Lions. Because of their tendency to stampede straight into the ocean whenever they spot a human, we have to tread very lightly and avoid certain portions of the island so that we don’t cause any unnecessary disturbance.
We are now observing some of the highest counts of Zalophus ever recorded on the Farallones since we began the census in 1970.
They have even disrupted communications between our weather station and house! Usually, we can monitor the wind speed and direction from the comfort of the living room, but the connection was lost when the herds of Zalophus started crawling around the weather station. Most likely, a wire has been ripped loose from the base of the tower by all of the jostling furry bodies.
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| Part of the Marine Terrace Zalophus Horde next to our weather station (seen in the upper left corner). |
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| View from the front steps of our house.
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| Aerial view of the Marine Terrace herds. Usually the Zalophus stay down near the shoreline, but here you can see hundreds of them hauled out all around the helo pad. |
This year, California has seen an enormous number of Sea-Lions being stranded on its beaches. Wildlife rehabilitation centers have been overrun with sick and starving Sea-Lions that have washed up and been brought in for treatment. The phenomenon is extensive enough that it has been picked up by many mainstream news agencies:
High numbers of strandings are thought to be an indicator of an impending El Niño, as hungry and starving individuals flee the overly warm and food poor waters to the south. During the last event in 1998, California saw 2,500 malnourished Zalophus wash ashore, and what followed was the most extreme El Niño event ever recorded.
We may be in store for many more Zalophus invasions in the coming years. Global climate change is predicted to increase the frequency and intensity of
El Niño events, as explained by a study discussed in this article:
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| A stranded Zalophus pup and concerned human bystanders on a Port Hueneme beach in Southern CA. |
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| A marked individual from San Miguel Island, which likely made its way here to the Farallones in search of food. We have been resighting a lot of marked Zalophus from San Miguel this year. |
So, in the meantime, as we sit here surrounded by these noisy, furry harbingers of El Niño, you can enjoy some Zalophus portraiture from around Southeast Farallon Island:
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| Zalophus pup near the Sea-Lion Cove blind. |
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| A seemingly smiling adult male at North Landing. |
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| An adult male at East Landing, showing a bit of Zalophus drool. |
