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A study published in the journal Behavioural Processes on 8 July 2025 found Himalayan monals in Uttarakhand shifting their calls to higher frequencies where roads, tourists and pilgrim traffic create noise.
Researchers from Hemwati Nandan Bahuguna Garhwal University compared the roadless Madmaheshwar Valley with the road-served, crowded Chopta Valley inside Kedarnath Wildlife Sanctuary.
Passive acoustic monitoring recorded calls without human presence; quantile regression showed noise explained 73.4% of the variation in peak frequency at the 95th quantile.
Traffic and crowd noise sits at low frequencies, so pitching calls higher lets the bird escape the masking band - evidence of acoustic plasticity.
The authors flag a risk to mating calls but stress that effects on breeding and survival are not yet established.
Vehicle and crowd noise is concentrated at low frequencies, where it drowns out calls of similar pitch. Birds that can raise pitch or volume push their signal out of the masking band - a behavioural adjustment known as vocal plasticity.
Simple Analogy: Raising your voice to a higher pitch to be heard over a rumbling generator.
The Uttarakhand university whose zoology researchers designed and ran the acoustic study
The protected area where the recordings were made; the largest protected area in the western Himalaya, created to protect the Himalayan musk deer
Maintains the Red List on which the Himalayan monal is assessed as Least Concern
The Himalayan monal is a Schedule I species, which carries the Act's highest penalties for hunting and trade regardless of its globally Least Concern status.
Kedarnath Wildlife Sanctuary was notified in 1972 under this framework; regulating traffic and visitor noise inside a sanctuary is a management power that flows from it.
Kedarnath Wildlife Sanctuary lies in the Chamoli and Rudraprayag districts of Uttarakhand, in the upper Mandakini and Alaknanda catchment of the Garhwal Himalaya. The two study valleys sit inside it: Chopta, on the motor road that carries pilgrims towards Tungnath and Chandrashila, and Madmaheshwar, which has no road and far fewer visitors. Beyond Uttarakhand the monal ranges west through Himachal Pradesh - it is commonly seen in the Tirthan Valley of the Great Himalayan National Park, a UNESCO World Heritage Site - into Jammu and Kashmir, and east to Sikkim and Nepal.
GS Paper 3 > Environment > Conservation, biodiversity and pollution
General Awareness > Indian wildlife, state symbols and protected areas
Leaving autonomous recorders in the field to capture animal sounds over long periods without an observer present to disturb behaviour.
The drowning out of an animal's signal by background noise occupying the same frequency band.
Seasonal movement up and down a mountain rather than across latitudes; the monal drops to about 2,000 m in winter.