A recent study published in Scientific Reports has shed light on the unique nasal structures of proboscis monkeys and their role as visual and acoustic signals of health and status. The researchers examined the structures in the skull to gain a deeper understanding of these enlarged noses.
Proboscis monkeys, native to Borneo, are known for their large, bulbous noses that hang past their mouths. The purpose of this strange feature has long been debated. Some theories suggest that it serves as a visual sign of health and status to potential mates and rivals, while others propose that it helps the monkeys produce loud sounds.
Using 3D surface models of adult proboscis monkey skulls, the researchers compared the size and shape of the nasal cavity and aperture with those of other monkey species. They also examined tooth wear to determine if older adult males had larger nasal apertures.
The findings revealed that male proboscis monkeys have a different nasal cavity shape compared to females and other monkey species. The shape allows males to build up resonance in their nasal cavities, enabling them to emit deeper and louder calls. The nasal aperture shape also differs between sexes, with males having a unique opening shape that allows for higher intensity sounds to be emitted through the nose.
Furthermore, the study found that older adult males have larger nasal apertures than younger adult males, supporting the idea that the large noses act as a visual signal of maturity and status.
These findings contribute to our understanding of how nasal structures in proboscis monkeys evolved for both acoustic and visual signaling. They also highlight the potential for using close examinations of skulls to gain insights into primate social behavior.
