If you’re reading this on your computer then you’re probably within reaching distance of them. Go anywhere amongst the public and you’ll notice that a lot of people are wearing them. Headphones and earphones are becoming more and more commonplace throughout our lives.
Some particularly sophisticated versions can even suppress environmental noises and enhance the sounds coming from their attached device. This detaches us from the surrounding world. Apart from missing captivating bird songs and the whispers of leaves, this may also put us in danger. We become oblivious to the signals outside our little headphone-insulated words. We’ve learned not to pay attention.
However, it may be of consolation that this is not merely a result of our electronically-enhanced era, but a by-product of evolutionary development. For we are not the only ones who suffer this learned deafness – we may be in the company of whales, such as the humpback.
Toothed whales are heavily dependent on echolocation for hunting and navigating. When a whale makes sounds, they bounce off their surroundings; these echoes return in patterns and allow the whale to understand its environment.
Many modern navies use low-frequency sonar signals which may interfere with the whales’ communication and echolocation, negatively affecting their survival. To address this problem, navies attempt to gradually increase the signal intensity in the hope that initial lower frequency is strong enough obtain the attention of whales, but weak enough so as not to damage their hearing or interfere with their communication. This strategy is termed ‘ramp-up’.
However, a recent study under the aegis of the Universities of Iceland and St Andrews showed that humpback whales can develop tolerance to ramp-up. Using suction cups, the research team managed to attach multi-sensor tags to 13 whales in the Barents Sea. On a sonar-emitting ship they then approached the whales, before increasing the sonar frequency and recording the whales’ behaviour.
It was found that the first ramp-up caused five whales to move away from the sonar source. However, the second ramp-up did not cause a similar avoidance. The only whale that moved away from the sonar on both occasions was a female whale with a young calf. Unsurprisingly, mothers tend to avoid unfamiliar signals that may potentially harm their progeny.
The results may indicate that whales will only react to the novelty of the ramp-up, and then a second exposure will not have the same effect. This could also suggest a variation in behaviour stemming from the small sample size. However, perhaps the initial exposure to the test signals damaged the hearing of the ‘avoiding’ group, and so the second signal was ignored. Or perhaps only the whales that had an already low risk-aversion could be tagged in the first place?
Even though, like most research, this study raises more questions than it answers, it highlights the importance of man-made activities on the habitats and behaviours of our fellow animals with whom we have a lot in common.
This article was written by Alina Gukova and edited by Sam Stanfield.