Dawn usually brings a chorus from gibbons — high, piercing wa-oo and wa calls that ring through the canopy as individuals and pairs establish territory and reinforce social bonds. But in a stretch of Malaysian forest hemmed in by housing and a nearby highway, researchers noted an unusual quiet: the resident white-handed gibbons were not producing their characteristic morning songs with the same regularity.
The study focused on groups living close to human development and roads and compared their dawn singing behaviour with that of groups in less disturbed areas. In one pair frequently observed by the team, identified as Mambang and Walinong, mornings were noticeably quieter; the pair produced far fewer songs than counterparts not subject to the same level of traffic noise.
Authors of the research say the findings point to a potential role for anthropogenic noise in altering primate vocal behaviour. As roads and housing fragment forest habitats, traffic hum can mask acoustic signals or change the way animals time and perform vocal displays, with consequences for communication across the group and between neighbouring groups.
The study’s authors call for further work to establish the mechanisms and wider effects of noise exposure on gibbon populations. Understanding whether reduced dawn singing affects territory defence, mate attraction or social cohesion will be important for conservation planning in landscapes increasingly dominated by roads and development.