Scientific name: Alouatta caraya
Country: Argentina, Bolivia, Brazil, Paraguay, Uruguay
Continent: South America
Diet: Leaves - folivore, fruits - frugivore, flowers. In the Zoo, they are given fresh leaves, mixed fruit and vegetables, granary bread, nuts, sunflower seeds and specially made primate dietary supplements.
Food & feeding: Herbivore
Habitats: Tropical rainforest, tropical dry forest
Conservation status: Least concern
Relatives: Uakari, common squirrel monkey
Description: Male and female howler monkeys are very different from one another. Only the male black howler is actually black at all, the female is blonde in colour (this difference is known as sexual dimorphism). The sexes differ in weight too: male weighing about 6.7 kg and females about 4.5 kg. They have a long prehensile tail, which they use to grasp branches whilst they are feeding and moving through the trees, and also to anchor themselves when sleeping. The hairless underside of the tail is sensitive to touch and enables the tail to feel what it is gripping. Howlers have enlarged throats, due to an extra-large voice box, to see why, read 'Keeping In Touch'.
Lifestyle: Howlers spend almost all of their time in the tree-tops, feeding on various sorts of leaves. They rarely come down to the ground, although in very dry conditions they may come down to find water. They are active during the day (mainly morning and evening) and make their way through the forest canopy in large slow moving groups.
Family & friends: Howlers usually live in social groups of up to 30 animals, although 5-8 in a group is more common. Several females will help to look after a single baby (called allomothering), carrying, grooming and protecting it, and even males will help out too, although young males are not allowed to do so, as they can sometimes harm the baby. In the morning, shortly after dawn, all the monkeys in a group take part in a chorus of howling. They prefer to stay away from other groups, although they do not defend a strict territory.
Keeping in touch: Howler monkeys are so called because of their amazing howling calls, which can be heard by humans up to five kms away. The calls are so loud because the monkeys have a special voice box and a pouch in the throat that amplifies the sound a bit like the horn on an old gramophone. Both sexes call but the male's voice is much louder and deeper. The call enables individuals to keep in touch with their group - and more importantly lets other groups know where they are.
Growing up: Pregnancy lasts roughly six months and one young is born, which is carried underneath the mother. The young are weaned at around 1.5 years of age and live to approximately 20 years of age.
Howler monkeys spend as much as 80% of the daytime resting. This means they are possibily one of the least active monkeys in the world.
Conservation news: As with many other species in South America, although they are not officially threatened with extinction, their habitat is being steadily destroyed and there are perhaps only 100,000 surviving in the wild now.
European zoos have a managed breeding programme for the species, which is coordinated by Bristol Zoo Gardens.