Noise pollution, generally an unintended byproduct of urbanisation, transport and industry, is a key characteristic of human development and population growth. In some cases, it is produced intentionally, for example when seismic surveys are being carried out using powerful airgun arrays to explore and map the seafloor, or active sonar, which uses sound waves to detect objects in the ocean.
All of this noise – whether intentional or not – has the ability to alter the acoustic environment of aquatic and terrestrial habitats. This can have a dramatic effect on the animals that live in them, perhaps even driving evolutionary change as species adapt to or avoid noisy environments.
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 ma.ting.
Scientific interest in the effects of noise pollution on wildlife has intensified over the past decade and we are now developing a better understanding of how noise can impact behaviour, population and community level processes across a range of animal species. Using experimental and observational approaches to characterise and explore the specific effects of different noise sources, the evidence generated from these studies is considerable, particularly among songbirds and marine mammals, which rely heavily on sound and vocal communication.
We now know, for example, that the foraging, vocal behaviour and physiological st.ress of cetaceans – whales, dolphins and porpoises – can be impacted by ship noise. This is of particular concern for species such as the en.d.ang.ered North Atlantic right whale that inhabits coastal US waters that experience very high levels of shipping traffic. Furthermore, in addition to shifts in distribution and vocal behaviour, military sonar has also been linked to the stranding of cetaceans.
In terrestrial habitats, bird diversity and abundance has been shown to decline as a result of chronic noise levels around cities and along roadways. A number of species have demonstrated adjustments to their vocal behaviour in an attempt to adapt to the cacophony of human noise. Urban great tits for example, are able to raise the frequency of their calls to reduce acoustical masking by predominantly low-frequency urban noise, while European robins adjust the timing of their singing to coincide with quieter periods in the city. Meanwhile, black-chinned hummingbirds and house finches appear to actively select noisy areas near active gas wells to avoid nest predation by more disturbance sensitive species. Also, A separate study, published in the journal Behavioral Ecology, looked at how female Mediterranean field crickets, Gryllus bimaculatus, make ma.ting 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 cli.pped 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 ma.te, 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 se.xu.al selection and s.ex.ual 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.”