Crane Named Walnut, Who Chose Smithsonian's National Zoo Worker as Her Mate, Dead at 42

"I’ll always be grateful for her bond with me," the bird's keeper, Chris Crowe, said in a statement

Walnut — a crane at the Smithsonian's National Zoo and Conservation Biology Institute, who chose one of the establishment's workers as her mate — has died. She was 42.

The Washington, D.C.-based attraction announced Walnut's death through a news release earlier this week.

"Staff at the Smithsonian’s National Zoo and Conservation Biology Institute’s (NZCBI) campus in Front Royal, Virginia, are mourning the loss of Walnut, a white-naped crane who became an internet sensation for choosing one of her keepers as her mate," the zoo wrote.

According to the National Zoo, Walnut was considered "geriatric" for her species as she lived far past the normal life expectancy for white-naped cranes kept in human care. (The organization said 15 years is the average lifespan.)

Walnut died in early January after zookeepers noticed she wasn't eating or drinking. Despite attempts to aid her, Walnut died naturally at an animal hospital while surrounded by the animal care team. A necropsy revealed renal failure as the cause of death, per the zoo.

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Related: Bird 'Bachelorette' : Meet the Rare Female Crane Who Chose a Man Named Crowe as Her Mate for Life

Walnut was born in 1981 and was named after a local restaurant’s popular walnut pie, according to the National Zoo.

In 2004, when she was brought to NZCBI’s Virginia campus, Walnut formed a bond with keeper Chris Crowe, who artificially inseminated her after he mimicked how male white-naped cranes at the organization interacted amid their breeding season.

In the years to follow, Walnut went on to give birth to eight offspring, many of whom "reached adulthood," per the zoo.

“Walnut was a unique individual with a vivacious personality,” Crowe said in a statement. “She was always confident in expressing herself, an eager and excellent dancer, and stoic in the face of life’s challenges. I’ll always be grateful for her bond with me."

He added: "Walnut’s extraordinary story has helped bring attention to her vulnerable species’ plight. I hope that everyone who was touched by her story understands that her species’ survival depends on our ability and desire to protect wetland habitats.”

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