Thursday, December 28, 2006

Christmas presents

We're picking up the pieces, like many in the Bay Area, in the wake of the after-Christmas storm that blew across the islands with 50+ knot winds. Here, the gusts buffeted the house so heavily that it shook. We woke up thinking it was an earthquake. The gale-force winds peeled siding from the houses and sent flying everything that wasn't tied down, including the large, heavy covers to our water catchment tanks. Happily, enough rain fell during the storm to add another few inches of fresh water to our cistern storage.

All of us here on the Farallones wish the best holiday cheer to the many folks who have supported us during the past year. The rich marine life here in the Gulf of the Farallones has attracted a human community that appreciates the Farallon Islands and the wealth of natural resources that exists here, and many help us with our research on this lonely rock perched at the edge of the continental shelf.

We made a great feast for the solstice with the groceries our Farallon Patrol coordinating angel, Brandy Johnson, arranged to be delivered on the 'Chelsea Lee' out of Sausalito. After big seas and high winds scrubbed our scheduled weekend Farallon Patrol run, skipper Harry Andrews and his crew Brett and Chris graciously rearranged their schedules, making a weekday dash to the islands during the one day of decent weather in the week of the 17th. We depend on these volunteer skippers of the Farallon Patrol who use their own boats to keep the island biologists fed, and delivering parts so we can keep our self-sufficient power and water systems running. Thanks Brandy and Farallon Patrol skippers and crew.

We received an early present the week before, when Brandy and Albertha arranged for Jared on the crab boat 'Bright Future' to deliver a cell phone to the island during a period when our radio communications were down and we were cut off from the mainland. Thanks Brandy, Albertha and Jared.

Many of the working boats of the charter boat fleet support our research on the Farallones by transporting critical equipment or personnel to/from the islands during their fishing/crabbing/shark- and whale-watching trips. Special holiday greetings to Mick and company on 'Superfish,' as well as the folks on 'Butchie B.,' 'California Dawn,' ' Wacky Jacky,' and the boats of the Oceanic Society and SF Bay Whalewatching. Thanks to everyone in the charter fleet. Thanks also to and Ron on 'GW' for checking our buoys.

A big year-end thanks also goes out to Rick, Steve, Ernie and the rest of North Coast Divers for being the most enthusiastic crane installers and maintainers we've ever had the pleasure of having on the island. You guys obviously appreciate the Farallones, and that makes all the difference.

We on the island are especially grateful this winter for the kind gifts from two special Santas, Joan Lee and Margaret Lewis.

Francine at Clairol also sent us our annual gift of product to mark the elephant seals with. Thanks Francine and Mary.

Of course, we must also thank Joelle and Jesse at the Refuge, and the Sanctuary folks as well for all that they have done this past year to make our research on the Farallones a success.

Wednesday, December 20, 2006

Bulls on the Beach

Elephant seal males that are sexually mature are called bulls. At the beginning of each breeding season, bulls arrive at the Farallones and establish their dominance hierarchy through displays of their mass and nose size, bellowing, and occasional fights. The highest-ranked bull is called the alpha, and he defends the largest harem (group of females). The rankings are fluid, and challenges occur daily. The payoff for the males comes at the end of the breeding season, when the cows they have been defending for a month wean their pups and become sexually receptive. The bull mates with each cow just before she returns to sea, leaving her pup on the beach as a weanling. Let's take a look at the main contenders for alpha bull status on the Farallones this year.

Nero became the alpha bull early last season by deposing JD, the previous alpha bull. Nero is the bull of Sand Flat, the largest harem on the Farallones with 97 cows last year. He's not the most massive male around, but his nose is enormous. Harem-organized species usually have a sexually-selected body part that acts as a signalling device to other members of that species to transmit information about sexual maturity and dominance. For elephant seals, the proboscis (nose) says it all. When Nero inflates his nose and bellows, the other males quickly move away.

Don Francisco is a veteran male who held a small harem last year on the Marine Terrace. He successfully defended this group from the constant incursions by satellite males. Last year he stayed away from Nero and contented himself with his 16 cows. We'll see if this year Don is still happy on the Terrace, or if he will challenge Nero.

Puffy is a newcomer to the Farallones, he was first seen this year, already an adult, and has established himself on Mirounga Beach. There are usually about 35 cows in this harem, but it is not a great location for the pups, over half die each year due to crowding and high swells washing out the small beach. Not a great investment in future gene survival, but about the same payoff as the Marine Terrace. Puffy is pretty large, he may make a move on the Sand Flat harem, but his nose just isn't up to Nero's caliber.

Bedlam Boy is a big satellite male who orbits the periphery of Sand Flat. Nero can't control the entire harem at all times, so satellite bulls like Bedlam Boy keep lesser males cleared away from certain portions of the harem's edge, never engaging the alpha directly, always ready for an opportune moment to mate with a cow while Nero is preoccupied on the other side of the beach. Bedlam may challenge Nero later, but thus far he has retreated every time Nero trumpets.

Brendan is still too young to claim a harem of his own, but he has been hanging around, sparring and harassing bulls for the last few years. He's earning his fighting chops and learning the terrain for future years when he will have the mass and the nose to defend a harem.

Still missing from last year's class of males are Altamont, Eeyore and Charlie H. Perhaps they are still foraging to get that bit of mass that will put them over the top.

Monday, December 18, 2006

Back to the Elephant Seals

December 2 marked the annual turnover of biologists from fall to winter crew at Southeast Farallon Island (SEFI). From mid-August until early December, PRBO researchers spent their time watching for white shark attacks from Lighthouse Hill and monitoring the hundreds of species of birds that stop over at the Farallon Islands on their fall migration. Now, the last of the fall migrant birds have moved on and the sharks have made their way elsewhere. The winter biologists have arrived and set up camp to continue PRBO’s important long-term (30+ year) research on the ecology of the fascinating northern elephant seal.

December is the beginning of the breeding season for northern elephant seals, one of five species of pinnipeds (a group of animals that includes seals and sea lions) at SEFI. Northern elephant seals breed on western North American islands from Guadaloupe Island of Mexico to the Farallones and some coasts (such as Point Reyes and San Simeon). The genus Mirounga, which includes northern and southern elephant seals, are the biggest pinnipeds in the world, with males typically reaching 3,500 pounds and some topping the scales at more than 5,000 pounds! See the picture of Rusty, one of our larger males (but not yet a bull): since he won't eat for more than 3 months while he is on land, he is saving his sleeping nearly all day long!

Before the adult elephant seals arrive for the winter breeding season at the Farallons, they’ve been out at sea for several months, foraging mostly for squid off the coasts of Washington and Alaska thousands of miles from their breeding and molting grounds. Because they travel back and forth twice per year – once to molt and once more to breed – elephant seals make the longest known annual migrations of any mammal in the world.

While at sea, elephant seals spend a surprising amount of time deep underwater. Scientists have discovered that these wonders of evolution spend 90 percent of their time diving, typically for about 20 minutes each dive, and coming up for air for only 2 or 3 minutes before heading back down again. The seals have a number of adaptations that enable their bodies to withstand the high pressures deep underwater. In fact, depth helps them to store fat more efficiently because their metabolism slows down due to the cold and water pressure at depth – they even sleep deep underwater.

By some estimates, females gain a kilogram a day while out at sea. They are trying to fatten up for the two month-long fasts they will make, especially for the winter breeding season where they will lose up to half their body weight nursing their hungry pups.

During the fall most of the elephant seals on SEFI are immatures, which are generally less than about 4 years old. The picture below shows two immature elephant seals hanging out together. The graph shows the average annual numbers of adult female (dashed line) and immature (solid line) elephant seals on the island – you can see how many immatures are here in the fall, which is why it is also the time of most shark attacks.

To date, we’ve had 6 pregnant cows arrive at SEFI, but no pups yet. This is in contrast to last year, where we already had a pup born on December 8 (the earliest ever recorded here). A "harem" is beginning to form at Sand Flat, with Nero – last year’s reigning bull there – fighting off the other smaller males for his right to mate with these females once their pups are weaned. But that is a long way off and new big males are arriving every day. Will there be a bull that dares to challenge Nero? Here, Nero announces his presence to the others with a loud, resonant snort through his massive nose.