They’re the sopranos of the forest, so what’s silencing the gibbons’ morning chorus? — SkimNews
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- Benjamin Galea, a final-year PhD student at Universiti Sains Malaysia, recorded white-handed gibbon morning calls at three Malaysian sites in 2023 and 2024 during wet and dry seasons, finding a clear inverse relationship between background noise and calling frequency.
- Highway-adjacent gibbons called in only 36% of recordings, compared with 71.4% for a secluded beachfront group and 84.6% for a hiking-trail group — and within each site, odds of calling dropped further as background sound rose.
- Nadine Ruppert, associate professor at Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, warns that persistent human-generated noise interferes with songs that serve territorial, mating and social functions — calling it a potential intrusion into "a very important part of their lives."
- When the highway gibbons did vocalize, 93.3% of their phrases occurred in solo rather than duet context; Galea speculates traffic noise may make it harder for the bonded pair to hear and coordinate with each other.
- The hiking-trail group widened their vocal bandwidth when vehicles became loud — a possible compensatory adaptation — yet still sang more often than the beachfront group, likely because neighboring gibbon groups prompted more territorial calling.
- Galea notes the highway gibbons may have simply shifted earlier, before the study's 6am start time, on days when recordings began mid-song — an offset that could itself disrupt resting, foraging, and contact with groups still inactive.
- The white-handed gibbon is listed as endangered by the IUCN, with its population believed to have declined more than 50% over the past 45 years; Malaysia has no recent population estimate, and isolated forest fragments persist inside Kuala Lumpur.
Why it matters: For an endangered species whose numbers have dropped more than 50% in 45 years, losing their morning chorus means more than quiet mornings — it erodes the pair coordination, duet singing, and territorial signaling that peri-urban gibbon populations scattered across Malaysian forest fragments depend on to persist.
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