An icon of the most well-studied killer whale population on the planet will probably no longer be part of it, as Granny, the world's oldest known killer whale, has not been seen since last October and is now presumed dead.

The Center for Whale Research, a non-profit group that has conducted orca survey in North America's Pacific Northwest for four decades, first reported Granny's death last weekend on its website.

Ken Balcomb, who has led the center's orca study, wrote on the website that he last saw Granny on Oct. 12, 2016, as she swam north far ahead of the others.

"Perhaps other dedicated whale-watchers have seen her since then, but by year's end she is officially missing from the Southern Resident Killer Whale population," he wrote, "and with regret we now consider her deceased."

Estimated to be over 100 years old, the orca's official name was J2.

Granny, one of the most beloved of her species by whale-watchers, avoided being sold to a marine park in the 1960s because even then she was considered too old to be shipped off.

After that, the whale went on to lead a pod of orcas for another half century.

The population of the endangered killer whales is now estimated to be 78 as of Dec. 31, 2016, according to the center, which is based in the U.S. State of Washington.

source: Xinhua