A pair of king colobus monkeys (Colobus polykomos) has arrived at Zoo Zürich, where the primates have been living in the ape house since early August. In the future, they are expected to move to Ndoki Forest, the zoo’s major new habitat for species from West and Central Africa, including western lowland gorillas.
Their arrival is particularly significant from a conservation perspective. The king colobus is classified as Endangered on the IUCN Red List, while the population managed through the European Endangered Species Programme (EEP) remains small. According to figures released by the zoo, only 57 individuals are currently held across 14 institutions. Zoo Zürich is now among the institutions participating in the programme.
Almost no thumbs — and for good reason
One of the most striking features of the king colobus can be seen on its hands: the thumb has been reduced to little more than a small stump.
Far from being a disadvantage, this is an adaptation to life in the West African rainforest. King colobus spend much of their lives high in the canopy and are highly skilled climbers. The reduced thumb helps prevent the hand from becoming caught as the monkeys move rapidly through branches, while their tail, which can measure almost a metre long, assists them as they travel through the treetops.
The pair at Zoo Zürich is eventually expected to move to the future Ndoki Forest, a 29,000-square-metre habitat planned for the lower section of the zoo. Both its indoor and outdoor areas will feature living forest, including trees reaching heights of up to 25 metres, and will accommodate several threatened species from West and Central Africa, including western lowland gorillas.
A digestive system with something in common with cows
The king colobus has another unusual adaptation. Its diet consists mainly of leaves — a fibrous and difficult-to-digest food source.
To process them, these monkeys have a multi-chambered stomach in which specialised bacteria help ferment plant material and break down cellulose. Although colobus monkeys are not ruminants, the system shares some similarities with the digestive process found in cattle and is relatively unusual among primates.
There is an energetic cost to this specialised diet. According to Zoo Zürich, king colobus spend around two-thirds of their day resting, sleeping, sunbathing or simply remaining inactive, conserving energy while their digestive system processes their leafy meals.
Youngsters are born white
King colobus are social primates, generally living in groups consisting of one or two males, several females and their offspring. During the first weeks of a youngster’s life, care is not necessarily provided by its mother alone: other females in the group may also help protect and look after the young.
Newborns are particularly conspicuous because their coats are completely white, making them easy for members of the group to see against the green forest canopy. Their fur gradually develops the characteristic adult colouration as they grow.
Habitat loss and hunting put the species under pressure
The situation in the wild has deteriorated significantly. Deforestation and intensive hunting for the local bushmeat trade have contributed to a sharp decline in king colobus populations. Poaching, illegal logging and mining continue to place pressure on the species, including in some protected areas.
King colobus also reproduce relatively slowly, with females generally giving birth to a single youngster approximately every two years. The coordinated management of the population through the EEP therefore aims to maintain a sustainable and genetically healthy population under human care.
The new pair at Zoo Zürich will eventually become part of Ndoki Forest, bringing a species highly specialised for life in the West African canopy into one of the zoo’s major future habitats.
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