There are about 160 monkeys living in Gibraltar in two main areas. About 20 of them at Apes' Den can be observed closely. However, the largest pack resides in the Great Siege area. 
 
Adult Males (Over 7 years)

These are the large monkeys, with big narrow faces. There are usually 4 at the Apes' Den with 4 more nearby.
 
Adult Females (Over 4 years) 
 
Smaller than the males, they have unmistakable black/grey beards on their chins and sexual swellings on the rumps.
 
Infant/Juveniles (1-4 years)

Male and female youngsters can often be seen playing together. 
 
Babies

These have black fur until about 4 months old. They are vulnerable, so please keep your distance! 
 
Behaviour (things to look out for)

Pouting
A warning to keep your distance.

Tooth Chattering
They do this to calm down and make-up after confrontations.

Grooming
Keeps their fur clean and is a social activity. They spend about 20% of their day grooming each other. At stressful times adults may grab an infant, hold it between them and tooth-chatter. This behaviour, unique to Barbary Macaques, is thought to help keep peace in the group.

Infant Care
Babies are born every summer after five to six months gestation. Most group members can be seen playing with, grooming or resting with infants, regardless of their relationship to them. Often females are content to let other 'aunts' help care for the babies after the first few days. Look out for a common grouping of a baby, mother and 'aunt'.

Male Barbary Macaques are unusual amongst primates in that they take a friendly, close interest in infants. You can often see males carrying babies or keeping an eye on them. Sometimes this communal infant care causes stress, you may see pouting, threats and tooth-chattering when a mother disputes custody of her baby with an over enthusiastic baby-sitter.

Background

Male Macaques live for about 15 to 17 years and females live 18 to 22 years. Every birth and death is recorded by Sites Management and each ape is given an official name at birth.
In 1915 the Government provided money for the Army to feed the monkeys and reduce the roaming and marauding that occurred. Responsibility for the monkeys has now reverted back to the Government of Gibraltar. The monkeys often supplement their diet with a few wild plants and can sometimes be seen foraging in the early morning. The monkeys are used to people so you can get close to them. Some may even approach you, but please do not touch them, monkeys will bite if frightened or annoyed.

If you see only a few active monkeys on site at first, please be patient and look carefully at the cliff/trees where you will probably spot some more. They spend over 30% of their day interacting with visitors but remember, they are still semi-wild animals. They need time to rest and take part in other 'monkey activities', free from interference.