A baby dugong which became a national sweetheart after she was rescued near a beach in southern Thailand has died after ingesting plastic waste.

Biologists say a combination of shock and plastic consumption caused the death of the orphaned dugong named Marium, who captured the nation’s hearts when she was found lost and alone.

The eight-month-old large ocean mammal went viral after photos of her being hugged and fed sea grass and milk by veterinarians spread across social media.

Thailand’s Department of Marine and Coastal Resources (DMCR) dubbed her “the nation’s sweetheart”. Veterinarians and volunteers fed her up to 15 times a day and gave her health checks.

But last week, she was brought in for treatment in the artificial sea on Libong Island in Krabi province after she was found bruised.

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Experts believe she may have been attacked by a male during the mating season.

The dugong is a species of marine mammal similar to the American manatee and can grow to about 3.4 meters in length. Its conservation status is currently listed as vulnerable.

Jatuporn Buruspat, the director-general of the DMCR, said: “We assume she wandered off too far from her natural habitat and was chased, and eventually attacked by another male dugong, or dugongs, as they feel attracted to her.”

An autopsy showed a large amount of plastic waste in her intestine, which could also have played a part in her death as it led to gastritis and blood infection, Mr Buruspat said.

“She must’ve thought these plastics were edible,” he added.