Primate Rescue Center

How a Monkey’s Face Tells You About Its Social Life

Erika Fleury November 19, 2013

Monkeys have the most colourful faces of all mammals – and there could be a social reason why.

Researchers have found a distinct pattern between a monkey's facial colour and the society they live in.

Dr Sharlene Santana at the University of Washington examined 139 species of Catharrines, a group of Old World monkeys and apes from Africa and Asia.

image courtesy Daily Mail

To compare faces, Dr Santana and her co-authors conducted analyses of hundreds of monkey headshots photos from online databases.

Faces were subdivided into 10 areas that were used to record traits describing the hair and skin colour.

The study found that species that live in larger, more social groups and those that interact with other, similar species, have faces with more complex colour patterns than those that live in smaller groups.

These colour patterns have also evolved to be more complex when closely related species live within the same area, possibly making it easier to tell each other apart.

Geographic location and environmental factors also played a major part in the evolution of facial colours of the monkeys and apes.

Species that live closer to the equator in dense, humid forests were found to have darker faces than those who live in less-vegetated and dry areas further away from the equator.

When living in a shadowy forest environment, darker face colours could potentially help camouflage these primates so they go unnoticed by predators.

The research also found that only primate species living in Africa show these trends - potentially because environmental differences are more extreme on this continent.

‘Our study helps explain the evolution of two major aspects of primate facial diversity; colour patterning and darkness,’ said Dr Santana. ‘We demonstrate that a combination of behavioural and ecological pressures may underlie the evolution of outstanding anatomical diversity. These types of complex interactions are likely operating in many other mammal groups.’

In a previous study analysing facial colours and complexities of New World monkeys, Santana found monkeys living in dark forests had darker colours on their faces compared to those that live in different environments.

However, one of the social aspects of the latest study is the opposite of the results for New World monkeys; New World monkeys that lived in smaller groups tended to have more complex colour patterns than those who lived in larger groups.

The researchers are now hoping to find out what factors could cause the differences between New and Old World primates.

- Daily Mail

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