The smaller of the giant panda twins born in Washington, D.C.'s National Zoo over the weekend has died, the zoo announced Wednesday, illustrating the challenges of keeping panda twins alive.
"This is a hard loss for us," zoo director Dennis Kelly said at a press conference. "It's hard to keep these tiny creatures thriving."
The zoo's panda team had been managing the smaller cub "more intensely" since its mother Mei Xiang rejected attempts to continually swap the cubs in her care, according to the zoo's blog.
Captive panda twins are difficult to keep alive because the mother usually is overwhelmed by caring for two. So zoos have developed a strategy of rotating the twins between mom and an incubator every few hours.
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When it works, each baby gets enough time with its mother to be fed by her. If necessary, the zoo supplements her milk with a mixture of infant formula, puppy food, and water.
The demise of the smaller, weaker twin mimics what would happen in the wild.
"A fundamental rule of nature is survival of the fittest," said Marc Brody, founder and president of Panda Mountain, a nonprofit group that works to conserve and restore panda habitat in China's Wolong Nature Reserve.
"When a mother panda has twins in the wild, the mother will only care for the stronger cub, sacrificing the weaker baby to help ensure the more vigorous cub survives," said Brody, also a National Geographic grantee.