It was a busy day near Fort Bragg, California as officials from the Marine Mammal Center and Naked Whale Research (NWR) struggled to relocate a 25-foot (7.62 metre) orca that washed up dead on a local beach. The large male, thought to be one of the transient orcas that move up and down North America's Pacific coastline, showed no alarming external injuries or evidence of boat collision.

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Image: Naked Whale Research

"It was a long day," reports NWR director Jodi Smith. "Marine Mammal Center came up with a team to move the whale to higher ground so a necropsy could be performed." 

Skin, blubber and organ samples were collected, and saddle patch photos were sent out to several organisations in hopes of identifying the individual. Much like a whale shark's spots, and our fingerprints, every orca's saddle patch (the white spot just behind the dorsal fin) is unique to that animal and can be used for identification. "There’s no real obvious damage to the whale, but it's worth pointing out that this whale had a notable human interaction," says Smith. 

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Crab pot floats and rope were found wrapped around the animal's tail and right pectoral fin, creating deep grooves in its skin. "Looking at how fresh the animal was and how deep the lines were, our initial thought was that they were likely there pre-mortem – but we really have to wait for the official report to determine if the entanglement contributed to the whale's death," she says. 

The animal was not emaciated and had a thick blubber layer, which suggests it was able to feed properly. In fact, the team found a full harbour seal in the whale's stomach. Unlike resident killer whales, which feed mostly on lean fish like salmon, the more migratory transients prefer fatty mammals. "They expend more calories moving around and rely on their fat reserves," explains Smith. "We know that pollutants and toxins accumulate up the food chain, and are stored in the lipid (fat) layers. So the difference in diet can be huge in terms of toxin build up in these whales."

Samples have been sent to Humbolt State University for processing, and NWR expects an official report soon. We'll be updating this post as information comes in. 

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The whale's two-metre (6 ft) dorsal fin is removed by researchers. Image: Jeff Jacobsen/Naked Whale Research
Image: Naked Whale Research
Image: Naked Whale Research
Image: Naked Whale Research
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Image: Naked Whale Research
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A skin sample is taken from the whale's head. Image: Naked Whale Research
Internal organs and stomach contents are examined. Image: Naked Whale Research
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Image: Naked Whale Research
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Image: Naked Whale Research

Top header image: DeWaine Tollefsrud/Flickr