domingo, octubre 2, 2022
InicioOpinionSing softly, dear sparrow | Mint

Sing softly, dear sparrow | Mint

AAH refers to the sounds that animals make. Specifically, it suggests that these sounds arose in response to the habitats that animals occupy; that they travel better in their own animal habitats (“native”) than in others (“foreign”). It’s probably intuitive. After all, the parrot chirps to send a message to other parrots – a possible partner, a rival male. Obviously he wants this message to be delivered. Thus, he adapts the screech to the environment in which he lives. Take that same parrot to an unfamiliar place—in the middle of the Sahara Desert or a noisy factory—and the sound may not transmit as efficiently as it does in that particular area of ​​Mumbai.

Not so different from us humans, really. You would probably scream if you were in a factory, but you probably wouldn’t if you were at home with your family.

Be that as it may, biologists have tested AAH on various animal species that are vocalizers – birds, primates, frogs and others. Many studies support the hypothesis. But some cannot, or at best can only “partially match” it.

For example, I recently read two intriguing articles: one about listening to frogs in Chile, the other about three species of mongoose in Africa. The frog researchers found that “in northern communities (of their study area), local calls degraded more than foreign calls, while the opposite was observed in southern communities.”

As for mongooses (mongooses?), their “habitat type strongly influenced sound transmission, (but) vocalizations were not always best transmitted in their native habitat.”

But if there is only partial support for AAH in both cases, there is evidence that these animals can – as mongoose scientists have noted – “regulate their vocal behavior to compensate for environmental restrictions on the transmission of their vocalizations.”

I mean, they would probably scream too if they were in the factory. And this has consequences. University of Tennessee biologist Elizabeth Derryberry studied white-crowned sparrows in the San Francisco Bay Area. Their singing must be heard through the near-constant flurry of city noise—traffic and the like. She found that men, in particular, reacted to what she called “urban anger”: the noise, she suggested, “perhaps leads to increased territorial conflicts in urban areas.” (City sparrows respond to a sexually selected trait with increased noise aggression, Elizabeth Derryberry et al., Nature, May 14, 2018).

What if a noisy environment suddenly becomes quiet? Well, we all just had that experience. The worldwide coronavirus pandemic has brought human activity to a halt in a way that few of us have ever experienced. It made our cities much quieter than usual – for several months, to the point where we almost began to accept this relative silence as the new normal. Is there evidence that urban animals have changed their vocalizations as a result of this dramatic change, this new normal?

Actually there is. During the Bay Area pandemic, traffic and associated noise dropped to levels last known 50 years ago.

It was a ready laboratory for scientists to see if the animals’ vocalizing behavior had changed at all. So Derryberry jumped at the opportunity to study the reactions of white-headed sparrows. (Silent Spring Singing: Birds react to half a century of soundscape reversal during covid-19 lockdown, Science, September 24, 2020.

These were good birds to work on in this research endeavor. This is because the frequency of normal traffic noise is in a “range that interferes with the most efficient and effective” sparrow singing. Remove this interference, and voila – the frequency and style of sparrow songs have changed. Recordings showed that they were suddenly singing songs with “high performance” – that is, more complex – but at a noticeably lower volume. However, even though they didn’t sing as loudly, the much lower ambient noise meant that their songs could now be heard over longer distances.

Softer songs because the birds no longer had to compete with traffic noise. More difficult songs because, again, they didn’t have to “shout”. Thus, they could be more expressive, use a wider range of frequencies, even embellish their songs with flourishes and trills. Think about how you would sing if you had to be heard through constant and loud noise, you would probably lose a lot of nuance too. And you would return them if the noise was gone. now they sang songs, as they probably did before cars, and other trappings of modern times changed the soundscape.

The most interesting thing about this change was that it was not gradual at all. Sparrows “quickly fill[ed] most effective space for songs,” Derryberry wrote, showing that “behavioral traits can change rapidly in response to new favorable conditions.” This suggests that these birds have a built-in resistance to human-induced environmental changes, such as traffic noise. Reverse the changes and they seem to be able to quickly return to what should be instinct, should be genetic memory of behavior – in this case, songs.

There is evidence that male sparrows use their songs to defend breeding territories from aggressive bachelor sparrows. To this end, more complex songs are more effective.

Does this lead to less “urban anger” among sparrows? It’s not clear yet. And with the end of the pandemic, the background noise jumped again. But sparrow songs have not returned to their pre-pandemic forms. Why? it’s also clear: it could just be the sparrows born during the pandemic picking up on the more intricate songs their parents tweeted.

All this makes me wish I had recorded parrots.

Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his lunches. His Twitter handle is @DeathEndsFun.

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