The world famous Rock of Gibraltar is home to a unique population of Barbary macaques.
Although not strictly speaking correct, the Barbary macaque is traditionally called an ape, since it resembles one in having almost no tail. Barbary macaques (scientific name, Macaca sylvanus) are Old World primates belonging to the family Cercopithecidae. In addition to the Barbary and other macaques, this family also comprises baboons, guenons and langurs. The members of this family share several skeletal features, such as a narrow nose, hindlimbs longer than the forelimbs, and a tail (when present) that is not prehensile. Due to other anatomical features mainly related to dietary adaptations, this family is divided into two subfamilies. The macaques belong to the subfamily called Cercopithecinae. One of the characteristic features of this subfamily is the presence of cheek pouches in which the animals store food.
Today at least 20 different macaque species are known and the macaque genus is characterised by its diversity. One example is the tail: while in the Barbary macaque, the tail is almost not existent, the long-tailed macaque from Indonesia has a tail longer than its body. Between these extremes, all intermediate stages can be found. They have also developed diverse ecological adaptations. Macaques are found in more climates and habitats than any other primate except humans. The geographical distribution ranges from as far east and north as Japan to as far west as Morocco. But the Barbary macaque is the only one to occur in Africa; all other macaques are found in Asia. Furthermore, the Barbary macaques on Gibraltar are the only free-ranging monkeys in Europe.
As with many other primate species, the major threat facing Barbary macaques in the wild is the loss of habitat. Extensive logging of forests together with increasing use available land for grazing of sheep and goats, leads to both reduction and fragmentation of the macaques natural habitat. Thus, not only are populations diminishing in size, but those that do remain are becoming increasingly isolated, since migration between the individual sub-populations is no longer possible. Gene flow is thus limited and this in turn leads to genetic impoverishment and reduction of potential to adapt to further environmental changes.
Natural predation in the wild does not constitute a threat, although encroachment from expanding human populations causes disturbance, particularly from dogs and other animals associated with human settlement, and also increases risk of disease transmission. Additionally, hunting of Barbary macaques for use as pets and tourist attractions continues to be an additional drain on the few remaining populations of this species.
Distribution of wild Barbary macaques
In Algeria, Barbary macaques have disappeared from several regions in relatively recent times. Today, only 7 widely separated small subpopulations remain. These populations are completely isolated by distances of 50-200 km.
The Moroccan Middle Atlas population is the largest and probably most important in conservation terms. Unfortunately, since it is not protected as a National Park, this last remaining stronghold of the species may also soon be under threat .
The species is listed as vulnerable in the IUCN Red List
Barbary macaque habitat in Morocco A Barbary macaque in Morocco
The Macaques today
Today the number of Barbary macaques on the Rock of Gibraltar totals about 230 individuals living in 6 groups with group sizes ranging between 25 and 70 animals. The monkeys are managed by the Gibraltar Ornithological and Natural History Society (GONHS) and veterinarian expertise is provided by the Gibraltar Veterinary Clinic (GVC). The animals receive a daily supply of fresh water and vegetables, fruit and seeds as supplement to natural food resources (leaves, olives, roots, seeds and flowers) and are also provided with veterinary care. The animals are caught on a regular basis in order to check their health status. Additionally, body size, weight and several other measures are taken. Finally, the animals are given a tattoo number and a micro chip as a means of identification. But tattoos are not the only way to recognise animals. Barbary macaques quite often show particular marks, scars or spots which can be used as distinguishing features. All monkeys were photographed and the pictures together with individual characteristics catalogued. Cataloguing work is carried our by GONHS, and there are collaborative studies also with the Scientific Institute of Rabat-Agdal University, Notre Dame University, Indiana, USA, the University of Vienna, the German Primate Centre and the University of Zurich.
Once every year, a census is conducted in order to actualise data and monitor reproductive success of the whole population.
These demographic data are important for the management of the population generally, but also when it comes to the point of fertility regulation in selected individuals. Since Barbary macaque females reproduce well, the population on Gibraltar is steadily increasing, which in turn puts pressure on the limited habitat. Population control is therefore an essential part of effective management of the Gibraltar colony.