Closely linked primates in the west: among the most human-like relatives on the planet

The Western Chimpanzee, a fascinating primate species native to Liberia, Sierra Leone, Guinea-Bissau, and Côte d'Ivoire, is the focus of our latest "Species of the Week" series. Known for their black hair covering their entire body, hands, and feet, these intelligent creatures are genetically and behaviorally distinct from other chimpanzee species.

Western chimpanzees lead a complex social life, with both males and females mating with multiple partners throughout their lifetime. Females give birth after eight months of gestation to a single infant, which they will take care of until it reaches around four years old. Both sexes in western chimpanzee societies will adopt orphan infants, contributing to a more gender-balanced hierarchy than in a patriarchal society.

These primates are known for their remarkable intelligence. Washoe, a wild-born chimpanzee, learned 350 signs and passed them down to her son after being successfully taught sign language. Western chimpanzees also demonstrate tool use, such as making and using wooden spears for hunting, and collecting fermented alcoholic sap from palm trees in leaves.

Their diet is primarily fruit, but they also include hunting prey in their meals. Males western chimpanzees prey on other primates such as green monkeys, patas monkeys, and Guinea baboons, while females predominantly hunt Senegal bushbabies, accounting for 75% of their prey.

However, the Western Chimpanzee is critically endangered due to deforestation and the expansion of human agriculture. Enforcement of national and international laws remains an ongoing problem, putting these intelligent creatures at risk.

Despite the challenges, efforts are being made to conserve the Western Chimpanzee. The European Endangered Species Programme for chimpanzees, led by Pluháčková at the Ostrava Zoo, is actively working on chimpanzee conservation, including efforts for the Western chimpanzee.

Western chimpanzees have been observed engaging in behaviours that suggest a playful and competitive nature. They have been known to throw large rocks into hollow tree stumps or against trees, which is theorised to be a type of sport.

With a head-to-rump length of 77-96 centimeters and a weight of 47 kilograms for males, and slightly smaller dimensions for females, these chimpanzees are well-adapted to their forested habitats. Their teeth are adapted for grinding plants and tearing meat, reflecting their versatile diet.

The Western Chimpanzee is a remarkable species, with a rich social life, impressive intelligence, and unique behaviours. Conservation efforts are vital to ensure their survival and protect this fascinating part of our natural world.