Officials at ZooMontana announced on social media Tuesday that Simpson, a grey wolf rescued in 2020, has died.

The wolf was found abandoned by his pack near Condon, which is along the Swan River 80 miles north of Missoula, when he was around five weeks old. He was then brought to ZooMontana in June 2020.

Simpson was diagnosed with congenital hydrocephalus, which causes a buildup of fluid on the brain. He underwent multiple surgeries to drain the fluid, which prolonged his life, but zoo officials noted a recent decline in his overall health and energy. He was humanely euthanized.

The zoo has one other wolf, Onyx.

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Here's the full post from the zoo:

With heavy hearts, we share the passing of Simpson, our beloved grey wolf.

Simpson's story is one that we hold near and dear to us, and one that we will tell for years to come. Simpson was found abandoned by his pack near Condon, Montana, when he was thought to be about five weeks old. He was then brought to ZooMontana in June of 2020. After noticing some irregular behavior, such as clumsiness and poor eyesight, a trip to the vet determined that Simpson had a condition known as congenital hydrocephalus. This condition causes a buildup of fluid on the brain, which is something that Simpson was born with.

Upon this diagnosis in 2021, we asked for public help to raise funds for Simpson’s surgery. The outpouring of support and reassurance from many of you who have or know of someone who has this same diagnosis is something we will not soon forget. With your support, Simpson went to Washington State University’s College of Veterinary Medicine to have a shunt placed in his brain that would drain the fluid from his brain into his abdomen. This surgery was successful, and his original shunt lasted until just last year when the shunt dislodged. Simpson went through another shunt surgery closer to home in Bozeman with the help of Bridger Veterinary Specialists. He recovered well from this surgery, and we are so grateful for the additional time this surgery gave us.

Sadly, despite these efforts, Simpson’s condition continued to take a toll. In recent weeks, his caregivers noticed a decline in his energy and overall health. Surrounded by those who loved and cared for him most, Simpson was humanely euthanized.

His packmate, Onyx, now carries on as the sole member of our wolf pack. He will receive the utmost care and attention from our dedicated team as we move forward.

To everyone who followed Simpson’s journey, supported his care, and celebrated his life with us—thank you. You helped give him a story worth remembering. Our hearts are with you, and with the ZooMontana staff and volunteers who gave Simpson a life filled with love, dignity, and compassion.