A female panda usually abandons one of a set of twins and even the lucky one can find itself squashed by its clumsy mother. That meant Le Le needed help in panda parenting, so the zoo started a 24-hour monitoring and nurturing regime and a 27-year-old zoo technician, Liu Xuefeng, was drafted in to give her a hand.
"I don't have a favourite, but the first born is slightly bigger and can walk, so he seems very sweet. He likes to play with a football, and if he is excited he will head the ball," he said.
FOR AN exhausted Mr Liu, the days and weeks have started to merge into each other in the structured and repetitive business of keeping baby pandas healthy and happy. After previous twin births, the zoo always removed one of the cubs for permanent hand-rearing, but it usually died. With Le Le, the keepers tried a different approach.
One cub is placed with the mother for suckling while the other is in a separate room with human carers. The twins are switched every 12 hours and Mr Liu is one of the two people who cares for whichever cub is away.
HE WAS on days this week - the 7.30am to 7.30pm shift. In a small room below the zoo's panda enclosure is the wooden crib and mattress for the cub not with its mother. Mr Liu's day is similar to that of any parent, dominated by feeding, watching and playing.
Each baby panda now weighs about 7kg (15lb) a massive increase in weight since birth but it will be several more months before they have passed the most vulnerable stage and can feed themselves. Not wanting to tempt fate, the cubs will not be named until they reach six months.
The two baby pandas swap places each morning at about the same time as Mr Liu starts his shift. "I stroke the cub like a cat to wake him up," he said. One cub is fed and transferred to Le Le's enclosure, while the other one is brought out after a night with its mother to spend the day with Mr Liu.
"When being fed by hand, the cubs like to be hugged. When I hold the cub, he can fool around and sometimes they scratch me," said Mr Liu, whose upper lip bears the mark of the last encounter.
The same routines are repeated later in the day, with a mid-afternoon feed and a 9pm final snack to keep up the baby pandas' calorie requirements.
For the time being the two cubs just take liquids; not until about 14 months will they start to eat the pandas' staple diet of bamboo.
While the rest of the world goes dewy eyed at the sight of a baby panda, Mr Liu is utterly underwhelmed by it all. "There is nothing interesting in the daily work," he said.
"It is ordinary work that outsiders think is interesting."