The western tree hyrax's vocalisation is structured rather than random. It opens with slow, low, creaking or ratcheting notes, increases in tempo and pitch through a long build, and finishes in loud screams. The full sequence can run for a minute or more and carries a considerable distance through dense forest.
The function is territorial and social. Tree hyraxes are nocturnal and largely solitary in the canopy, where vision is nearly useless at night, so an unmistakable long-range signal does the work that scent marks or visual displays would elsewhere. Call structure differs between tree hyrax populations, and acoustic analysis has been used to argue for undescribed species within the group.
The animal is far better known by ear than by eye, and much of its natural history is thin. Population estimates depend on call surveys rather than sightings, activity budgets in the canopy are poorly documented, and the taxonomy of African tree hyraxes is unresolved, with more species likely than the current names allow.