The world's oldest known killer whale is missing and presumed dead.
The whale—named J2, though she was affectionally nicknamed Granny—was estimated to be more than 100 years old, BBC News reported. She was the star of a recent BBC documentary that chronicled biologists' study of her family of orcas, in order to look into female whales' menopause.
Only three mammals experience menopause: orcas, short-finned pilot whales and humans. The orcas, including Granny, have been the subject of a four-decades long study from the Center for Whale Research in Friday Harbor, Wash.
The center said Granny was last seen on Oct. 12, 2016, as she swam north ahead of others in her clan. As of the end of the year, she was considered missing from the area's killer whale population and is now officially considered deceased.
The research will continue, though without the study's most famous participant. "It was inevitable that this day was going to come, but it is very sad news," researcher Darren Croft of the University of Exeter in the United Kingdom told BBC News.
The number of whales in the population is estimated to be just 78 orcas, as of the end of 2016, according to the BBC. That's in part due to the fact that the number of salmon, which the whales feed on, is shrinking in the region.