A pack of 25 of the Barbary macaques have “run riot” on a beach, have broken into hotel rooms and have been caught scavenging in bins in the town centre.
The threat of attacks on humans and the possibility of the spread of disease has forced authorities to approve the cull “as a last resort”.
Ernest Britto, Gibraltar’s tourist minister, defended the plans for the cull, saying: “Children are frightened. People cannot leave their windows open for fear of the monkeys stealing. “Apes can bite, and contact with them runs the risk of salmonella or hepatitis.”
Vets are to track down the tearaways and put them down by lethal injection. Two have already been killed.
The Gibraltar population of the Barbary macaque – a monkey commonly referred to as the Barbary ape because of its stubby tail – numbers more than 200.
They attract hundreds of tourists every day to the areas around Apes Den and the Siege Tunnels at the top of the Rock.
Francis Cantos, the spokesman for the Government of Gibraltar, insisted: “This is being done as a last resort.
“The apes we are targeting are part of a breakaway group that are going into town and making a nuisance as well as posing health hazards.
“They’ve been spotted going through rubbish, vandalising property and stealing from people. They ran riot at the beach at Catalan Bay.”
The cull has the backing of many locals including staff at Gibraltar’s Caleta Hotel, where guests’ rooms were vandalised recently by apes looking for food.
However, the decision to destroy the rogue pack has been condemned by animal protection groups.
Helen Thirlway, the conservation and welfare director for the International Primate Protection League (IPPL) in the UK, said the monkeys were the colony’s most popular tourist attraction and the “needless slaughter has to stop”.
British soldiers are thought to have introduced the apes, natives of north Africa, into Gibraltar in the mid-18th century to use for shooting practice.
Local folklore has it that the colony would cease to be British if the monkeys were to leave.
Winston Churchill took it seriously enough to ship extra monkey from north Africa to Gibraltar during the Second World War.