Working from home during Covid-19 has brought noise pollution close to home, whether it’s your partner making calls within earshot or grinding coffee during your Zoom interview. Now research suggests the animal kingdom is also disturbed by the noise of humans and our gadgets.
As humans proliferate, we have penetrated deeper into wildlife habitats, creating a pervasive rise in environmental sound that not only directly affects the ability of animals to hear but indeed communicate. Emerging research suggests noise pollution, caused, for instance, by traffic, interferes with animal behaviour, including cognition and mating.
In an attempt to capture the impact of traffic sounds on cognitive performance, researchers gave adult zebra finches – a species of diminutive songbirds native to Australia – a series of foraging tasks.
The birds were either in a relatively quiet laboratory environment or treated to traffic noises designed to simulate a series of cars driving past 20 to 30 metres away.
To test inhibitory control, a skill useful for maintaining attention required to solve a problem, the songbirds were given access to a clear cylinder laid horizontally with food inside. The researchers assessed whether the birds would succumb to their intuitive response to reach in or take the more efficient route of going around the side that was left open.
The next task was lid-flipping to access food. This was designed to measure motor skills and object manipulation, which are critical for foraging. After that, the birds moved on to associative colour learning – where their ability to discriminate between different coloured lids to determine which contained the food reward – was tested. The researchers also tested spatial memory, which is crucial for remembering the locations of food sources, territorial boundaries and potential mates.
Finally, they evaluated the birds’ skill in learning from each other. A few “demonstrator” birds learned how to pull out twine knots to access food hidden within wooden blocks, and others were judged on their ability to emulate the task.
All tasks apart from colour association learning were negatively affected by traffic noise, the researchers wrote in the journal Proceedings of the Royal Society B.
“We weren’t really sure that we would see such a strong effect,” said study author Christopher Templeton, an assistant professor at Pacific University, Oregon, US.
“These are birds that … live in big colonies, they’re all talking all the time making quite a big ruckus. So, to see that just the simple act of hearing cars drive by is enough to really keep them from being able to perform on these tests is pretty surprising in some ways.”
A separate study, published in the journal Behavioral Ecology, looked at how female Mediterranean field crickets, Gryllus bimaculatus ̧ make mating choices under different acoustic conditions.
Males attract females by performing a courtship song by rubbing their wings together.
“In this this species, specifically, we know that the male courting song is linked to immune-competence, so they [the females] know if they have a particular high quality song they are better at surviving diseases,” explained lead author Dr Adam Bent of Cambridge University, who carried out the study as part of his PhD at Anglia Ruskin University.
To test the impact of different noise conditions, the researchers paired female crickets with male crickets whose wings had been clipped to mute their singing prowess. Then, the crickets were left to interact in ambient noise conditions or artificial noise conditions or traffic noise conditions.
Then, an artificial courtship song was played when the males attempted to court the females.
Females are typically on the hunt for multiple quality males, so the quicker they can mate, the better it is, so they can move on and find another mate. The more mates they have, the greater the offspring, and higher the likelihood that offspring survive.
In the context of ambient noise, the females mounted the males much sooner and more frequently when paired with a high-quality courtship song, the researchers found.
But the high-quality song offered no benefit in the white noise and traffic noise conditions. “The data … shows that females are unable to detect subtle differences in the song, and that means they are unable to show any difference between males that perform a high-quality song and males that perform a low-quality song,” said Bent.
“On an individual level this will have knock-on effects, potentially, to their offspring, and their offspring’s viability. But on a population level, mate choices are a really powerful mechanism of sexual selection and sexual selection drives evolution,” he suggested.
“So, by having mate choices disrupted in this way, it could vastly change the course of evolution of the species.”