A string of recent incidents has intensified concerns that some groups of Barbary Macaques are out of control.
It is a problem that has long affected locals in some parts of the Upper Town, but it is now hitting the tourist trade too.
At the Caleta Hotel on the east side and The Rock Hotel on the west, balconies have become primate playgrounds. Many visitors feel intimidated by the animals.
And where once the monkeys stayed outside, tourists often now find them rummaging for sweet food inside hotel rooms.
For the hoteliers, the situation poses an uncomfortable dilemma: while the monkeys attract visitors to the Rock and therefore business for hotels, they say the present situation is unsustainable.
"It's now become problematic and we are worried for the safety of the guests," said Stephen Davenport, general manager at The Rock Hotel.
