It is well known that animals are affected by human noise pollution. For example, dark-eyed junco birds that live in cities sing both louder and with a different song than their countryside counterparts. However, human noise pollution is not contained to cities, and even our oceans are filled with the noise from ships, motorboats and jet skis.
Most research into human noise pollution has looked at how animals deal with communicating when there’s more noise than what they’re used to. However, noise can disrupt more than just an animal's ability to communicate. Have you ever been in a bar, and had trouble enjoying your food, just because the music was too obnoxious? Or, if you happen to like pounding beats with your pizza, what about when you're in a restaurant and an electric piano version of a Celine Dion song comes on and it makes you feel so physically sick that it's hard to digest your soup.
While these aren't exactly the kind of problems that other animals face, having human-made noise might impair animals' ability to find food by stressing it out, making it less hungry, or more directly through interfering with the animal’s ability to detect its food.
A recent study compared the effects of human noise on two fishes: three-spined sticklebacks and European minnows. The researchers played a recording of ships to the fish while they were foraging to see how their behaviour differed from when they foraged with a playback of silence. When being played the sound of ships, both species of fish ate less of their food (the waterflea, Daphnia) and were startled more often than when they had quiet. However, it seems that the noise disrupted the behaviour of the sticklebacks and minnows in different ways.
When the sticklebacks were played the ship noise, they made more errors while they were foraging, whereas the minnows were just less motivated overall to feed.
If a fish has this kind of disruption to its feeding it can mean that it then eats more when it is quiet, or spends more time foraging overall. This can in turn increase its chances of being eaten by a predator, if it is forced to search for food during the time or in the areas that predators hunt.
In an unexpected twist to this tale, anthropogenic noise (for example of ships), can actually affect the behaviour of the invertebrate prey (like the waterflea prey of these fish) as well as the fish themselves. Such noise can make invertebrates like these waterfleas more alert to danger, and therefore harder to catch by their predators. However, in the current study at least, the sticklebacks seemed to be making more errors to do with attacking non-food items instead of the waterfleas rather than the waterfleas being better at escaping them.
As this experiment was carried out in the lab, it’s not clear how reliably it translates to natural conditions. For example, it is possible that fish that are constantly exposed to anthropogenic noise habituate to it and ‘learn to live with it’. Studies in the future will need to address how wild fish populations deal with the anthropogenic noise they are exposed to, and whether it alters their behaviour in a negative way.
Stickleback: Jack Wolf
Waterflea: Duncan Hull
Voellmy, I.K., Purser, J., Flynn, D., Kennedy, P., Simpson, S.D. & Radford, A.N. (2014) Acoustic noise reduces foraging success via different mechanisms in two sympatric fish species. Animal Behaviour, 89: 191-198.