With a starved frame, the approximately 30-foot marine mammal was reported dead earlier this week off an Anderson Island shoreline, biologists said.

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Biologists are investigating why a juvenile humpback whale became stranded and then died on Anderson Island earlier this week, a sad result of what scientists say is a growing humpback population in Puget Sound.

With a starved frame, the approximately 30-foot marine mammal was spotted Sunday on the southeast side of the South Puget Sound island, prompting a search for the humpback, biologists said.

The search proved unsuccessful, and on Tuesday the whale was reported dead off the shoreline near Thompson Cove, according to the National Marine Fisheries Service, which is part of the National Oceanic and Atmospheric Administration.

Scientists with multiple agencies, including the Washington Department of Fish and Wildlife (WDFW) and Cascadia Research Collective, flocked to the area to investigate the whale’s death.

Officials say an initial necropsy determined the animal wasn’t sick from an underlying disease, and severe emaciation was the leading cause. Further analysis will give them more details.

Scientists believe the humpback had been swimming in a winter breeding area before recently returning to Puget Sound, according to Cascadia.

Officials believe the whale may have been the same animal seen a week earlier off Whidbey Island and Edmonds.

Scientists took the whale’s carcass to the WDFW facility on McNeil Island, where scientists will collect its bones as the animal decomposes, NOAA Fisheries said.

Humpback whales spend summer months building up fat in cooler waters, such as Puget Sound, and then migrate to warmer seas in the winter for mating.

Scientists say the recent whale death is a result of a growing humpback whale, or megaptera novaeangliae, population in Puget Sound.

Kristin Wilkinson, of the National Marine Fisheries Service, says the stranding of humpback whales in Puget Sound is something scientists have only begun to see recently, likely the result of a growing population.

Last June, a 35-foot-long humpback whale was found dead in Bremerton.

Roughly two months later, a stranded humpback whale died on a West Seattle beach.

Researchers believe there are more than 18,000 humpbacks in the North Pacific, compared with 1,500 when whale hunting was banned in 1966.