Molting

This month's column in The Cambrian:

The seals look like something terrible is happening to them. Their skin is peeling off! Talk about splotchy skin. But for northern elephant seals, it’s the normal, annual molt.

The adult females are on the beach in April and May, accompanied by juvenile seals of both sexes.
Elephant seals, like only one other seal (the Hawaiian monk seal) molt their skin annually in a few short weeks. All other seals molt, but most do so gradually, so it isn’t as noticeable.

A new skin layer forms beneath the old skin. Blood supply to the old skin ceases and the old skin peels off in pieces. Scraps of it skitter across the beach. Friends of the Elephant Seals docents have samples of it to show visitors. Children enjoy handling it. Adults seem to be more dubious, extending a cautious finger for a touch.

The adult males are gone, and this year’s weaners have left on their first migration. The beach is full of seals, but the drama of the breeding season has passed. There are actually more seals on the beach in May than during the breeding season.

The seals stop eating when they are on the beach at the rookery, fasting for that four to six weeks it takes for them to complete their molt.

Females gain weight
When the females were last on the beach, at the end of lactation in February, they were thin. They’d converted their blubber to milk to nourish their pups. They’ve spent the past two months eating and gaining weight.

Now, while they are molting, other invisible, but significant, changes are happening beneath the skin. Before returning to the ocean and leaving her weaned pup on the beach in February, each seal mated to conceive a pup for next season. That fertilized egg divided a few times, then stopped developing. The tiny embryo continued to float free in the uterus, dormant.

The mother-to-be spent the next two months or so feeding freely in her ocean home. When she returns to the beach in April to molt, her body makes the changes needed to have a pup next season.
After she’s finished molting and returns to the ocean, that embryo implants in the uterine wall and begins normal development. Delaying development of the embryo gives her time to gain weight before starting the demands of the next pregnancy.

Staying at sea
Gestation is 7.5 months. When they leave the beach after molting, the expectant mothers will remain at sea until they return to give birth next January.

Delayed implantation is part of a complicated life cycle. Spending most of the year solitary in the water requires different strategies for breeding. So far as their lives are understood, males and females don’t encounter each other except on the beach during breeding season. This is how the species has worked it out.

The 2015 breeding season produced about 4,900 live young-of-the-year, a 9 percent increase over 2014. Fewer females and fewer pups were actually born, but more survived, thanks to the mild winter weather.

Read more here: http://www.sanluisobispo.com/2015/04/22/3599145_elephant-seals-shed-their-skin.html?rh=1#storylink=cpy

Weddell seals in the Ross Sea

Wildlife photographer John Weller concluded the story he shared with Cambrian readers last week at his Sunday afternoon presentation, sponsored by Greenspace — The Cambria Land Trust. In last week’s Cambrian, he told about being in an underwater ice cave in Antarctica’s Ross Sea. About 60 people turned out to hear him tell the story.

John Weller's photo of a Weddel Seal in the Ross Sea.

After he descended through a hole in the ice, he entered an ice cave. A second, smaller cave, its entrance only waist-high, beckoned. He climbed through the low opening.

A beacon of light penetrated a crack in the ice shelf above, creating a gleaming beam, illuminating bottom-dwelling sea creatures, in motion as they climbed on a pile of rocks. Weller unloaded his tripod and camera, no simple task under water, to set up for a particularly beautiful photograph, when he was struck from behind and thrown to the ocean floor.

With his head whirling, and vision blurred, Weller tumbled to the sea floor. A cloud of silt mushroomed up around him. Losing air from his dry suit, he gazed up toward the sea ice, panic setting in.

Above him, he saw a Weddell seal floating, looking down at him. Weddell seals aren’t usually aggressive toward humans, but they are big wild animals. They can be 11 feet long and weigh more than 1,300 pounds. Not the animal to be enclosed with in a small ice cave on a bad day.
Weller scrambled to pull himself together and get out of that cave, but picking up the weight of the tripod and camera without adding air to his dry suit  made him crawl toward the exit instead of swimming. Recovering from his daze, he added air to his suit so that he could move better, without losing his equipment.

He made his way out of the cave, past the seal, back to the surface and the safety of the ship. Uninjured but shaken by the experience, he wasn’t sure whether this close call would disqualify him from future dives. Eventually, he shared it with Antarctic ecologist Dr. David Ainley, his mentor on the voyage. By that time, he had become convinced that the seal had never touched him — it had blasted him with a sound so loud that he didn’t recognize it as a noise.

Ainley was intrigued. One of the mysteries of Weddell seals is how they capture prey such as the Antarctic toothfish at depths of more than 800 meters. Seals commonly bring the large fish to the surface by the lip, otherwise uninjured.

Do seals stun their prey with loud sounds blasts? Weller’s experience was consistent with being the target of a 190-decibel sound blast. Ainley is now investigating that possibility. And unlike toothfish, Weller surfaced to tell the tale.
 

Read more here: http://www.sanluisobispo.com/2015/04/22/3599229_photographer-weller-antarctica.html?rh=1#storylink=cpy

Ross Sea photos

Internationally acclaimed photographer John Weller was drawn to the plight of Antarctica’s Ross Sea after learning this place – the last large intact marine ecosystem left on earth – was under attack by an unsustainable fishery. His decade-long journey to tell the Ross Sea story brought him there four times, including over 50 dives under the ice. He’ll share photographs and stories from his book The Last Ocean on Sunday afternoon, 3-4:30 pm, at the Vets Hall. Please join us to celebrate the incredible natural history and get involved in the movement to protect the Ross Sea.

Pollution, climate change and overfishing have intrinsically changed every other part of the world’s ocean. Researchers estimate that humans have caught as much as 90 percent of the top ocean predators since 1950.

“The ocean seems infinite and immutable,” Weller said. “But the truth is horrifying. We’ve pushed ocean systems to the brink of collapse worldwide. The fact that we have damaged the ocean so deeply should be of grave concern to all people. The Ross Sea story is not just about a fish, or the incredible organisms that live at the edge of the world. This is our story – the story of our struggle to become sustainable.”

But Weller believes that conservation in the Ross Sea could be the start of a tide change in international marine management. Right now a massive marine protected area in the Ross Sea is under discussion at the highest levels of government around the world. It would be the biggest marine protected area in the world.

“Ross Sea protection would require the agreement of 25 nations. Imagine all these voices speaking as one in defense of the ocean. It has the potential to both protect one of the world’s last great places, and set the stage for sweeping changes in how we manage oceans all over the globe. There is a lot riding on the fate of the Ross Sea.”

Despite feeling continually humbled by the extremes of the Ross Sea, Weller says the most humbling moment occurred on a dive under the ice:

“Under the ice in McMurdo Sound, there’s a series of underwater ice caves formed by crushed sea ice. The entrance to the cave complex is an archway 10 feet tall. Beyond that is a cathedral of light.

‘As I entered this underwater cave, time stood still. It was as if I were entering an ancient place. And it is. Those caves form every year, and have for eons. I swam through the first chamber of that cave and was about to turn around, when I saw another cave, with an archway about waist high. I peeked through that archway and saw a photograph I knew I needed to take.

‘I swallowed some fear and pushed myself through the archway into the second chamber of the cave. There, I saw a photograph I will never forget. Benthic creatures were arranged on a pile of rocks on the sea floor. A crack in the ice ceiling looked like a plume of blue smoke. I was carrying a tripod and a camera, so I put it together, working with my camera to get this photograph.

‘All of a sudden, there was a smack. It felt like something had hit me in the back of my head with a hammer. My vision blurred, and my muscles tensed. I rotated in the water, lost air from my dry suit, and found myself on the sea floor completely dazed, and with a building sense of panic…” 

He lived to tell the tale, which he will conclude at his talk Sunday afternoon.

Weller’s visit is sponsored by Greenspace. $10 suggested donation at the door. He will sign books for sale after his talk.

Molting

The beach is filling up with seals returning to molt. It's adult females and juveniles of both sexes who are on the beach.

Most of this year's pups have left on their first migration. The seals on the beach now are a full year old and older. It's easy to see the old skin peeling off.

The adult males have left to regain the weight they lost in three months on the beach during the breeding season. This one shows how thin they get.

He'll soon regain that weight and bulk up to his fighting weight, feeding along the coastal shelf along the Canadian and Alaskan coast.