Thursday, April 23, 2015

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.

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