The walker looks up, alerted by a series of “How! How! How!” and the rustling of leaves. Dark humanoid figures rapidly disappear across the treetops. They must be monkeys. At first it looks like there are five or six coming towards him. Given their size and their way of moving, the walker thinks they must be red-faced spider monkeys, also called Guiana spider monkeys.

It’s important not to make any noise, there are increasingly few opportunities to observe them in the north of the country and the walker wants to make the most of it. Leaning against the trunk of a tree, he raises his binoculars to his eyes and waits. He can soon make out the big monkeys. The red skin of their face is in sharp contrast with their uniformly shiny black hair.

Watching the spider monkeys moving about overhead is a fine acrobatic spectacle, and the group swings from one branch to the next hanging by their arms and tails. Their tails play a key role, and they use it for balance and as a fifth limb. Spider monkeys have prehensile tails, with a thick-skinned tip able to seize branches and objects as a hand does. The man soon gets to see how useful this unusual adaptation to life in the trees is for these arboreal animals. Whilst two individuals have already gone past without seeing him, two others have spotted him and stop directly above his head. Hanging by their tails they start calling out frenetically, warning the rest of the group which flees noisily on either side of the trail. But the two stay there and carry on vociferating. Soon they start taking hold of branches that they rip off and throw towards the man watching them from below. With sticks raining down on him he has to beat a retreat. This comical scene might seem to come straight out of a Tintin adventure book, but it is one that is well-known to regular walkers on the forest trails of French Guiana.

The red-faced spider monkey (Ateles paniscus) is a remarkable species and one that symbolises the forests of French Guiana, but it is disappearing from certain forests. It plays a major ecological role in regenerating the undergrowth, has an important place in the cultures of French Guiana, and was long a source of food for people living from hunting. But it is also a species that is sensitive to any disturbance to its habitats and is unable to resist intense hunting pressure due to its biological characteristics. The species has been fully protected in French Guiana since 1986 due to a decline in population numbers.

An animal that is essential to regeneration of the forest

Spider monkeys live in groups of between 15 and 20 individuals that often move around in subgroups so as to improve the efficiency of their hunting for food. The group splits up into several units of between 2 to 5 monkeys. This way they share out the resources of their vast territory, which can stretch over the 300 hectares. Whilst the species eats primarily ripe fruits, its diet can also be supplemented with seeds, flowers, and leaves. It has been established that red-faced spider monkeys eat over 200 species of plants, including over 170 fruits. This diverse diet means the spider monkey is the sole means by which many trees are propagated. Uneaten fruits and seeds are left on the ground, as are those which have been digested and excreted, and they end up germinating. This is the cycle of life. The species therefore plays a key role in the regeneration and diversity of the forest.

A slow reproductive cycle

Like many other large mammals the red-faced spider monkey has a slow reproductive cycle. The females reach sexual maturity at the age of 4 or 5 years and only give birth to one infant after a long 7-month gestation period. The young monkey suckles until the age of 3 and is dependent on its mother for several years.

Hunting – the spider monkey’s number 1 problem

This slow growth rate explains why the spider monkey is sensitive to hunting, which is the main threat affecting populations in all the areas where the species is found. In French Guiana it is still poached despite regulations protecting it, and it is a highly prized game because of its large size. Some communities claim the right to hunt it at certain intervals for personal consumption or cultural use, such as the formal end to the mourning period in the Bushinenge culture. But the spider monkey has been badly hit by human pressure in French Guiana as elsewhere. It has been estimated that if the numbers removed from the population exceeds 2% to 3% per year, then this is likely to endanger it and result in significant drops in its density. Programmes to monitor hunting carried out in conjunction with the hunters themselves over a period of several years in several traditional forest villages in French Guyana have shown that the numbers removed often exceed these critical thresholds. These results corroborate those of other studies carried out elsewhere in Amazonia for other spider monkey species. Increases in the size of villages, settlement, conflicts in forest usage when sylvatic communities are obliged to share their hunting zones with loggers for instance, and exploration for gold means that these great apes are endangered by hunting, even of the traditional kind, nearly everywhere.

The spider monkey and the fragmentation of its habitats

But hunting is not the only threat to these great apes. Logging, if poorly managed as can be the case in several Amazonian countries, has an important impact on fauna. The excessive felling of certain tree species and damage done to others, the fragmentation of forests, and the creation of access roads result in a modification to the actual structure of the forest. This leads to a whole cavalcade of consequences for the entire ecosystem. And there is no way that monkeys, one of the most arboreal animals, are able to avoid them.

Some of the factors that have an impact on monkeys are, briefly: the breaking up of their territories, difficulties in gaining access to food resources (and even a modification of these resources), and conflict between groups. It goes without saying that all of this weakens the populations, especially as logging access routes very often lead to the emergence of new hunting zones for man. Studies carried out in French Guiana have shown for that matter that the spider monkey is unable to maintain its population in forests that have been disturbed.

With the increased number of inventories of the territory in sites subject to various pressures, it has been possible to estimate that spider monkey populations are under threat in nearly one third of the country. In addition to the need to control poaching, protected areas also have an important role to play by making it possible to maintain healthy populations in untouched forests. But managing forests outside the nature reserves and parks is also essential. Conserving species such as the spider monkey with large territories and low densities is only possible with large-scale operations and the maintenance of corridors between the highly protected zones.