Dolphins shout to be heard over human-created ocean background noise

Dolphins have to shout at each other when trying to communicate as underwater noise has increased substantially because of increased human activity over the past decades.

Sound travels well underwater which exacerbates the problem. In preindustrial times the oceans were much quieter than they are today. Marine wildlife evolved in a quiet environment and therefore they are disturbed by the noise as it can reduce the ability to hear environmental cues which are vital to their survival.

Dolphins have to shout to be heard over human-made ocean noise.
Dolphins have to shout to be heard over human-made ocean noise. Image: MikeB at PoC.

Their attempts to communicate are being masked by human-created sounds. Sadly, the oceans have become noisy places. The study suggests that dolphins may be able to change the volume and length of their calls when working together to overcome this background noise.

Mammals rely on whistles and echolocation to hunt and reproduce. Noise made by humans such as drilling and shipping might affect their health as a consequence.

The study’s lead author, Pernille Sorensen from Bristol University said:

“Those same reasons that make sounds advantageous for animals to use also make them susceptible to disturbance from noise in the environment. Within the last couple of decades, we’ve seen a dramatic increase in human-made noise, and noise pollution in the oceans is no exception.”

In the study they observed two dolphins swimming in an experimental lagoon with recorders which captured the sound they made.

The dolphins had to work together to press a button within a second of each other according to The Times report of Friday, January 13, 2023.

When the researchers increased the levels of noise played from a speaker both of the dolphins compensated by changing the volume and length of their calls. And they swam closer together to ensure that they were coordinated when pressing the button.

When the noise was set to the highest level the dolphins’ success rate dropped to 62.5% from 85% when the noise was at its lowest level.

Sorensen, in commenting on this, said:

“This shows us that despite them using these compensatory mechanisms, the communication was impaired by noise.”

The two dolphins in the research project were used to living within a human caregiving environment but the researchers suggest that human-created noise could have the same effect on wild dolphins.

The findings were published in Current Biology.

The same problems exist with many marine species from zooplankton and jellyfish to whales with their attempts to communicate being masked by sounds that humans have introduced.

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