This is how noise pollution can harm animals

by Fay Clark and Jacob Dunn, Anglia Ruskin University

From construction projects to busy roads, aeroplanes and railways, human noise is everywhere. It is an invisible cause of stress, posing serious risks to human health and wellbeing. However, noise also harms animals living in close contact with humans, in homes, farms and zoos.

Noise is a distracting, scary or physically painful sound. The impacts of noise upon humans range from mild irritation to learning and memory problems, permanent hearing damage and heart disease.

Abnormally loud noise, such as at music concerts or construction sites, is controlled to protect human hearing. But noise is not regulated for other animals.

In our recent paper, we found a greater awareness and more understanding is needed into how noise harms pets, farm and working animals and zoo animals.

Research tends to measure how loud a noise is in decibels (dB). Decibels are easy to measure with a handheld device and form the basis of human health guidelines. But the type of noise source, frequency (pitch), rate and duration can also impact how noise is experienced by a listener.

Great apes have similar hearing capabilities to humans, but the rest of the animal kingdom perceives noise very differently. Hearing ranges from very high frequency ultrasound (>20,000 Hz) echolocation in bats and dolphins to very low frequency infrasound (<20 Hz) in elephants. The hearing range of humans sits right between ultra and infrasound.

Some invertebrates such as hunting spiders detect sound from vibrations with their tiny leg hairs. It’s difficult to tell how sensitive an animal is to noise but what’s most important is whether noise in their environment is within their hearing range, rather than if the animal has a high or low frequency.

What we know

Due to a lack of research, we don’t know that much about how precisely noise affects animals but this is what we’ve learnt so far.

Loud noise can permanently damage lab rodents’ hearing. We can assume this exposure is painful because rats exposed to loud noise behave differently with and without pain medication. Findings in lab rodent studies can be generalised to other mammals but there are known differences in hearing ability across different animals.

Wild animals suffer chronic stress, fertility problems and change their migration routes in response to noise. Confined animals are often exposed to high levels of human-generated noise which they cannot escape.

Research shows noise causes confined animals pain, fear and cognitive problems. For example in fish, vibrations from extreme noise can damage the swim bladder which in turn impacts their hearing and buoyancy. Pain and fear are strong indicators of poor welfare.

Inaudible noise (vibrations) can also hurt animals by physically shaking their internal body parts. Farm animals experience high levels of vibration during transport. Our research group at Anglia Ruskin University is investigating whether vibrations from construction work impacts zoo primates.

One noisy event such as a local music festival or extreme weather can trigger long-term fear in animals. The link between noise and fear has been well studied in dogs using recordings of thunderstorms.

This kind of noise sensitivity, which affects up to 50% of pet dogs, is triggered by unexpected noises. It makes animals hide or seek human comfort. Farmed hens exposed to vehicle noise and even music also freeze in fear.

Primates, birds and frogs can adjust in the short term to noisy environments by vocalising louder, similar to raising our voices at noisy parties. But the long-term consequences of animals needing to change their methods of communication hasn’t been studied.

Long-term exposure to loud noise reduces learning and memory ability in lab mice. The link between cognition and anxiety in humans is complex but generally speaking, high levels of anxiety reduce our ability to perform challenging tasks.

This could be similar in other mammals but there is not enough research to be sure. Studying noise in zoos is difficult because it’s hard to control other factors, like weather and visitor presence.

How to help

If your pet is stressed by noise, a range of treatments are available to calm or distract them including synthetic pheromones and enrichment toys. But prevention is better than cure.

If you take care of confined animals, pay close attention to human activities that generate noise (such as cleaning and gardening) and how the surroundings may reflect sound waves. Sound waves can be blocked and bounce back from materials like concrete, metal and glass, which makes the noise worse.

You can protect your pets during noisy events, like thunderstorms and firework displays, by providing extra spaces to escape noise. Some soft furnishings like pillows or blankets inside a den help absorb sounds. A pile of blankets to crawl under, even without a den, will help to block out noise.

Better regulation is needed to protect animals from construction work and noisy events. Animals don’t have a say in what building projects or music concerts go ahead but they can suffer the consequences.

Fay Clark, Research Fellow in Life Sciences, and Jacob Dunn, Associate Professor of Evolutionary Biology, at Anglia Ruskin University

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