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Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

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The Battles Begin

January 6, 2010

The genus Mirounga comprises the northern and southern elephant seals, the largest pinnipeds in the world. Our large northern elephant seal bulls on Southeast Farallon Island weigh up to 5,000 pounds – some particularly massive ones are even heavier. Northern elephant seals are highly sexually dimorphic, with males weighing 3 to 6 times more than the females. While smaller than their southern counterparts, northern elephant seal bulls have a longer nose and more pronounced chest shield of scarred and thickened skin. This chest shield is associated with fighting, and the nose is thought to act as a resonating chamber that amplifies their bellow to warn off other males.

Pink chest shield and large nose on Bubba.
Winter marks the season of bull battles as males compete to dominate the harems of females who have come ashore to give birth, nurse their pups, and breed. Rusty, our alpha bull last year, has returned and is holding the Sand Flat harem again, with 15 cows as of January 3, including Daniela, Kyra, Eone, and Lodi, and 7 pups. Kyra and Eone were both born on SEFI in 1999.

Kyra with her newborn pup on Sand Flat.

Flaccido Domingo is the beta bull on Sand Flat. Time will tell whether he challenges Rusty for the top spot.

Flaccido Domingo is second on Sand Flat, but wary of mighty Rusty.

Speaking of challenging for the top spot, the bull Bubba attempted to do so on December 31, leading to his demise. Rusty killed Bubba in a brutal, hour-long battle in which Bubba got stuck between two rocks in Log Channel Beach. This happened to Nero in 2007, when he was killed by Don Fransisco after getting wedged between the same two rocks.

Rusty and Bubba battle in Log Channel Beach.

Most elephant seal fights do not end in death, but occasionally when two bulls are closely matched, the winner will continue to batter the loser until he is permanently eliminated. The battle was a sobering reminder to PRBO biologists of the realities of nature and that life itself is at stake for these animals. You can view a part of the battle below, but be warned that it is not for the faint of heart.

The harem on the Marine Terrace of Sand Flat is small but growing. There are currently 3 cows and 2 pups, including new cow Shaye. McHammer, not quite a bull, is dominating this harem. He is 9 years old, born and tagged on the Farallons in 2001.

McHammer on the Marine Terrace.

Mirounga Beach has no pups yet, and cows so far have been just passing through. Felipe, nearly a bull, has been seen in Mirounga Beach. Similarly sized Mein Gott is biding his time on Lower Arch Terrace. McHammer, Felipe, and Mein Gott are known as “SA4” seals, or 4th-year subadults. The next step up is a bull.

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