VANCOUVER—Researchers say they suspect one of the oldest killer whales in the West Coast’s southern resident population has died.

The Center for Whale Research in Washington state says researchers have determined that orca J2, known as Granny, has not been seen since Oct. 12 and is believed dead.

The centre says in a statement on its website that it does not know what killed Granny, but she was believed to be at least 78 years old and was the eldest within the three family pods of endangered southern resident whales.

She was also considered the matriarch of J-pod.

The centre says with her apparent death, the pod now contains just 24 members, while the total number of southern resident whales has fallen to 78.

The loss of Granny comes less than a month after J34, an 18-year-old male member of J-pod, was found washed up on a Sechelt beach after apparently being hit by something, and the October death of J28, a female with a one-year-old calf.

Southern resident killer whales, which almost exclusively eat salmon and travel through the waterways of the Salish Sea, were listed as endangered in 2005.

The Center for Whale Research has studied southern resident killer whales for four decades.