He may look cute and cuddly but Gu Gu is out for revenge.
The eight year old giant panda was startled last year when a drunken tourist jumped into his pen and bit him on the back.
So this week, when a second tourist tried to join him in his pen, he took no chances and savaged the visitor - a teenage boy - by ripping flesh off his legs.
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Gu Gu may look cute and cuddly but he is a wild animal who can be violent, say zoo keepers
The 15-year-old boy, believed to be called Li Xitao, jumped over the 4ft 7in barrier to the panda enclosure "out of curiosity" at Beijing Zoo on Monday afternoon.
However, the startled 240lb panda responded by biting his unwanted visitor on both legs.
Emergency medical officials said the teenager was so viciously attacked, his bones were showing and chunks of flesh were left behind in the ambulance.
Gu Gu hit the headlines last year when he was bitten by a drunk tourist. Then, a man jumped into the bear's pen and tried to hug him but was bitten instead. The tourist retaliated by biting Gu Gu on the back.
This time, zoo keepers who were in the enclosure at the time of the attack, managed to lure Gu Gu away from the boy. However, they said the attack lasted two or three minutes.
Li Xitao is from Hebei province in northeast China and makes a living in Beijing selling recyclables he picks off the street. He was taken to Beijing Children's Hospital.
Gu Gu was later seen snacking on bamboo.
Zoo officials said pandas enjoyed an image of being cute and cuddly but were wild animals that could be violent when provoked or startled.
Staff at the zoo are considering new measures to prevent further incidents.
"We have to prepare against such behavior," said the director of the zoo management office, who identified himself only by his surname, Zhang. He added that visitors should "act properly when visiting." Police are investigating the incident although it is unclear whether the teenager will face criminal charges.
Panda bitten by drunken tourist takes revenge by savaging teenager at Chinese zoo | the Daily Mail
Why are some people so stupid?