The cetacean was discovered by passersby at the North Beach in Point Reyes National Seashore, about 15 miles southwest of Petaluma.
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The Sausalito-based Marine Mammal Center dispatched five scientists to do a necropsy on it on Tuesday, but it will take about two weeks before results are announced.
The whale had no broken bones, ruling out the possibility that it was struck by a vessel, the center said, but it did have bruising around its neck. Its stomach was full and its blubber was a healthy thickness, indicating that it had been healthy before its death.
Research assistant Barbie Halaska told The Press Democrat that most of the beached whales they study are too decomposed to determine a cause of death, but because this one recently died, they will likely be able to.
“The opportunity to perform a necropsy on a carcass in good condition like this will help contribute to our baseline data on the species,” Halaska said in a statement.
This is the fifth whale to wash ashore this year, which is typical, the center says—normally they see five to six each year, the Press Democrat reports.
There are about 15,000 humpback whales that live in the North Pacific, according to the center, and they feed between California and Alaska in the summer and as far as Japan in the winter.
At about 10 percent of their original population, humpbacks are among the most endangered whales, the center says, with 35,000 to 40,000 in the wild.
In recent years, however, more have been seen along the California coast.