Zookeepers are tricking a new panda mom of twins into thinking she's got only one cub, so both will survive.
In this BBC Earth clip, a new panda mother doesn't realize she's raising twins. According to the narrator, who is none other than David Attenborough, it's not unusual for pandas to birth multiples. What is unusual is for mama pandas to take care of more than one panda cub when she has. Normally, she'll abandon one (or more) of them so that the other will live. Attenborough says that it's thought that they don't have "sufficient milk or energy" to raise more than one, so they starve the unwanted cub(s).
So, in an effort to keep both pandas alive, zookeepers are playing the old switcheroo on the twins' mom, Lee Lee. They've been switching out the (OMG-they're-so-adorable) cubs up to 10 times a day and, so far, Lee Lee is none the wiser.