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A 2025 study found that Himalayan monal calls recorded in a noisier habitat had higher peak frequencies than calls in a relatively undisturbed habitat. The researchers also reported a slight increase in call duration. The comparison links vocal differences with habitat noise; it does not prove that noise alone caused them or that the birds have permanently changed their voices.
What did the study find?
The study, “Noise-induced vocal shifts in the Himalayan Monal (Lophophorus impejanus) vocal distribution in two different habitats,” was published in Behavioural Processes in August 2025. Researchers compared monal vocalizations and noise variables from an anthropogenically noisy habitat and a relatively undisturbed one, analyzing the measurements with quantile regression. The journal article record and its PubMed abstract describe the findings.
The clearest reported difference was in peak frequency: calls from the noisier habitat had higher peak frequencies, with the association appearing more pronounced toward the upper end of the vocal-frequency distribution. Call duration was also reported as longer in noise, but the authors characterized the difference as slight.
Where were the calls recorded?
The two study settings were in Kedarnath Musk Deer Sanctuary in Uttarakhand. The Indian Express reports that researchers used passive acoustic monitoring devices and a microphone across seasons, recording calls in Chopta Valley and the relatively quiet Madmaheshwar Valley. Chopta has a road and receives tourists, pilgrims, and other visitors; the report describes Madmaheshwar as comparatively undisturbed. It says the study captured hundreds of calls but does not provide a precise count in the account.
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The contrast therefore involves more than a noise meter reading: the sites differ in human activity and may differ in other ways, too. A two-habitat comparison cannot isolate noise from every other site-level factor.
What do the reported statistics mean?
The authors reported quantile-regression pseudo-R-squared values for peak frequency of 0.231 at the 10th quantile, 0.215 at the 50th, 0.454 at the 75th, and 0.734 at the 95th. These are model-fit statistics at different points in the frequency distribution. They do not mean that those percentages of birds or calls changed.
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The indexed abstract also reports that mean absolute error increased from 142.14 at q=0.1 to 185.49 at q=0.95. Taken together, the results indicate a stronger model fit at higher quantiles, but these statistics should not be read as a direct measure of how much an individual bird raised its call.
Why might noise be linked to a different call?
Human-made sound can overlap with animal vocalizations, making communication more difficult. A higher peak frequency could be one way calls differ in a noisier acoustic environment, but the study documents an association between habitat conditions and vocal traits rather than demonstrating the birds’ reason for calling differently.
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Noise in the reported setting was not attributed to tourism alone. Co-author Anand Kumar told The Indian Express that it comes from “transportation or the heavy footfall from the pilgrimage.” The report also describes roads and other human activity as part of the busier habitat.
Does this mean monals have permanently changed their voice?
No. The study compares vocal traits recorded in two habitats; it does not establish a permanent or evolutionary change. Nor does the comparison prove that noise alone produced the differences, since the sites may vary in other relevant conditions.
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The available reporting does not establish whether the vocal differences affect mating success, breeding behavior, or long-term survival. Co-author Rajeev Lochan described the mating exchange this way: “The male makes the mating call and the female responds to that call.” Whether the observed shifts change that exchange remains unanswered.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What does this mean for conservation?
The Indian Express reports that the researchers call for managing noise in heavily visited areas. That is a call to address noise, not to end tourism. The same report describes the Himalayan monal as globally Least Concern on the IUCN Red List, while noting Lochan’s warning that reliable local population data are lacking. A global status does not establish that every local population is secure.
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