Overview
Lively, watchful and highly vocal, the blue monkey is a familiar presence in many of Tanzania’s forested landscapes. Despite its name, its coat is usually slate-grey, olive or dark grey rather than truly blue, with a darker face and a pale band or patch across the forehead.
Blue monkeys spend most of their lives in the trees, moving confidently through the middle and upper canopy in search of fruit, young leaves, flowers and invertebrates. Fruit is particularly important in their diet, making them valuable seed dispersers that help regenerate and maintain healthy forests.
They live in social groups centred around related females and their young, usually with one resident adult male, although additional males may temporarily join during the mating season. Group size varies considerably and can range from around ten animals to several dozen.
Behaviour & How to Identify
Look for a medium-sized monkey with a long tail, dark limbs, a grey or olive coat and an expressive dark face. Many individuals have a pale or yellowish forehead patch, sometimes called a diadem, although colouring varies between Tanzania’s different regional populations.
Blue monkeys are mainly arboreal and rarely spend long periods on the ground. Their long tails help them balance as they walk and leap between branches, while their hands allow them to inspect fruit, leaves and bark with considerable precision.
Troops communicate through calls, facial expressions and body movements. Alarm calls warn others about predators, while softer vocalisations help group members remain in contact as they spread through dense foliage.
Interesting facts
They carry food in cheek pouches. Blue monkeys can gather fruit quickly, store it temporarily inside their cheeks and move elsewhere before stopping to eat.
They sometimes join other monkey species. Blue monkeys may travel and forage alongside red-tailed monkeys or colobus monkeys, potentially improving access to food and providing additional warning of predators.
Some females can live for more than 30 years. A long-running wild study in Kenya recorded female blue monkeys surviving beyond 33 years, although this should not be treated as the typical lifespan of every individual.