Colorful Primate Traits Ease Group Conflicts

Primate ornamentation is essential for both internal and external communication within social groups, according to a recent study. Published in Evolution Letters, the research found that male primates displaying vivid colors or intricate features are often found in species with overlapping home ranges. These striking traits may help to minimize aggression between different groups by allowing quick identification of rivals.

These ornaments are sexually selected characteristics that signal an individual’s genetic fitness, health, or physical prowess. Dimorphic traits, which highlight differences between males and females, can include colorful fur or elaborate body structures. Examples are the golden snub-nosed monkey’s lip wart and blue face, the mandrill’s bright facial features with a red nose and blue skin, the gelada baboon’s impressive mane and red chest patch, and the proboscis monkey’s large nose.

A study from the University of Zurich (UZH), conducted by Stefan Lüpold and Cyril Grueter from the University of Western Australia, reveals a fascinating connection between these traits and how primates engage with other groups.

Analyzing data from 144 primate species, including monkeys and apes, the researchers investigated how ornamentation correlates with home range overlap. They discovered that species with greater spatial overlap had more pronounced differences in ornamentation between the sexes. Males in these species were more likely to have distinctive features that separated them from females.

The study also found that species with significant home range overlap experienced fewer aggressive intergroup interactions, which can involve physical confrontations, displays of strength, avoidance, and vocal warnings. This implies that bright physical traits might play a role in reducing conflicts between groups by allowing them to assess potential rivals from a distance.

These results challenge the notion that primate ornamentation is only for intra-group competition for mates. Instead, they highlight the broader social context, demonstrating that ornamentation is crucial for navigating complex animal communication within and between groups.