Lanka, a 14-year-old sloth bear from South Asia, has been displaying worrying behaviour since her move to London from Warsaw Zoo three months ago.
She rocks from side to side in a motion that some animal experts have described as a classic sign of boredom.
But keepers have moved to dispel the worries of people viewing this strange spectacle by putting up signs around her two acre enclosure.
The sign states: "You may have noticed that the female sloth bear sometimes displays an abnormal `rocking' behaviour in front of doors. The keepers are trying to cure this with a wide variety of behavioural enrichment ideas".