The Oakland Zoo has lost Siskiyou, the matriarch of its six-member gray wolf pack.

“We are broken hearted to share the news that Siskiyou, beloved mother of Oakland Zoo’s gray wolf pack of six, was humanely euthanized today after our vet team discovered a large mass in Siskiyou’s abdomen during a routine annual examination at our hospital early this morning,” The zoo said just before 2 p.m. Wednesday.

The zoo said Siskiyou underwent a CT scan and the tumor was determined untreatable. Because of the pain and suffering, zoo officials made the difficult decision to euthanize her.

“Our hearts are with sweet Siskiyou, and the dedicated Animal Care team that cared for her with passion and love.”

Oakland Zoo statement

“Family is very important to wolves, and our animal care team decided to temporarily bring Siskiyou back home after her euthanasia to give the pack time to understand her passing,” the zoo said on social media.

Siskiyou came to Oakland Zoo in December 2017 from a conservation center in Montana. She was introduced to male gray wolf Sequoia. In May 2019 she gave birth to four healthy pups, and the pack has enjoyed their sprawling habitat together for the past four and a half years.

The zoo said staff will be watching the rest of the gray wolf pack closely as they absorb the loss of their matriarch.

“They continue to serve as ambassadors to their wild counterparts, educating guests about the complexities of human-wildlife conflict that wolves face in the wild. Our hearts are with sweet Siskiyou, and the dedicated Animal Care team that cared for her with passion and love.”