White-handed gibbons in Malaysian forests exposed to traffic noise appear to be producing fewer morning songs, according to recent research. These arboreal animals are known for their complex vocal techniques, which can travel over half a mile through dense forest canopies.
The study, conducted by Benjamin Galea, a PhD student at Universiti Sains Malaysia, found that gibbons living near a highway called in 36% of recordings, compared to 71.4% for a seaside group and 84.6% for a hiking trail group. The research, which is yet to be peer-reviewed, suggests that the greater the background noise, the less likely gibbons were to call.
Nadine Ruppert, an associate professor at Xishuangbanna Tropical Botanical Garden and a supervisor of the research, stated that gibbon songs are vital for communication between groups, territorial interactions, and social relationships. She noted that persistent human-generated noise could interfere with this important aspect of their lives.
Galea's research, conducted in 2023 and 2024, recorded and analysed calls from gibbons in three locations with varying noise levels. It is possible that the highway group avoided singing due to the loud traffic or sang earlier than the 6am to 1pm monitoring period. Singing earlier could help overcome noise but might disrupt resting, foraging, or coordination.
If background noise causes gibbons to avoid singing, it could affect their ability to maintain territory, attract mates, or warn of predators. Further research is needed to determine if this ultimately impacts their reproduction or survival. The white-handed gibbon is listed as endangered by the IUCN, with its population believed to have declined by over 50% in the last 45 years due to habitat destruction, hunting, and capture.