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Nature took its course Wednesday afternoon, when the smaller of the twin cubs that giant panda Mei Xiang gave birth to Saturday evening, at the Smithsonian National Zoo, died around 2 p.m.

At a press conference this afternoon, officials described the course of events leading to the smaller cub’s passing. Don Neiffer, the zoo’s chief veterinarian, said that despite pandakeepers’ efforts to swap the twins so they could spend equal time with Mei and also be monitored carefully by vets, the smaller cub failed to gain weight, had possible respiratory issues, and appeared weaker as of this morning. The precise cause of its death is not yet known.

“It’s obvious that we were prepared, but it’s not surprising we’re disappointed,” Neiffer told reporters. “We want to focus on what we have, which is a healthy panda [cub]. We remain very optimistic about that animal’s future.”

The larger of the two cubs, which weighed 138 grams at birth compared with the smaller panda’s 86 grams, appears “robust” and is in Mei’s care, Neiffer added; it’s vocalizing and “doing great.” The zoo previously reported issues with swapping the cubs during the past three days: Mei Xiang wasn’t willing to give up the larger twin so that keepers could let the smaller one bond with her.

“There’s been some misunderstanding that [Mei Xiang’s] been preferring one cub over the other,” Neiffer explained. “When the second cub was born, there was some frantic behavior on her part to balance and juggle these two kids at the same time. Mom never showed a preference.”

Keepers won’t know why the smaller cub died until autopsy results come back in the coming days. Brandie Smith, the zoo’s associate director for animal care, said the panda team followed best practices to optimize the cubs’ chances of survival, even enlisting a professional with panda-experience from Zoo Atlanta. They’re now making sure both Mei and the remaining cub “have everything they need.”

“Every giant panda in the world is important,” she said. “[It’s] part of the greater conservation story, that incredible feeling when you have these two beautiful, fragile, delicate cubs, and you have the awesome responsibility of helping a mother care for [them]—the superhuman effort.”

“When we realized the cub wasn’t going to make it, it was devastating.”

Original post:

The National Zoo has just announced that the smaller of Mei Xiang‘s twin panda cubs died around 2 p.m. this afternoon. “The larger cub appears to be strong, robust, behaving normally and is with mother Mei Xiang,” a press release states. Stay tuned for updates.

Photo by Darrow Montgomery