"She left them there, lying in the cold," said zoo spokesman Bart Kret.
The zoo initially kept the cubs in an incubator. But a keeper's tabby cat had just given birth to four kittens, and let the two panda cubs join the crowd.
One of the cubs was too weak and died Thursday.
The surviving cub is still smaller than the kittens, who were born three days before her. However, if she survives to be an adult, she will be slightly larger than a cat.
Kret said the cub will drink milk for about three months, after which she can start eating bamboo and fruit.
The cub doesn't have a name yet, but the zoo says that, through its adoption program, anyone willing to sponsor her will be allowed to name her.
The red panda is an endangered species that lives in China, Bhutan, Nepal, India, and Burma. It has a striped tail like a raccoon and is only distantly related to the much larger giant panda.
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