A Danish-Australian team of researchers have discovered in a new study that whales can suffer from disturbances caused by boat engines, even when the boats seem far away. Unlike humans, the creature's dominant sense is hearing, which is why even if boats keep their distance, the noise emitted from their engines could still reach them.
The researchers have found that because of these noises, the whales change course, dive, swim faster, breath faster, and could produce different sounds far from the usual. The authors of the study urge for the implementation of new guidelines for whale watching to keep boats from disturbing the whales.
The experiments were done in Exmouth Gulf on Australia's west coast. The gulf is known to have the largest population of humpback whales worldwide. The researchers used a drone to search for a mother whale and their calf and would bring their boat at a 100-meter distance from them.
The researchers achieved a total of 42 controlled exposure experiments of this kind. Furthermore, they recorded all behavioral activity of the whales from a high angle using the drone's camera.
They found that the resting period of whale mothers declined by 30%. Moreover, their breathing rate increased two-fold, and their swimming speed went up by about 37%. The researchers documented these findings using the highest noise emitted at a level of 172 decibels from the boat's engine at approximately 100 meters away from the creatures.
After the boat moved further away, the researchers noted that the whales then returned to their normal state of resting. The findings of the study were published in the online journal eLife on June 16, 2020.
Is Whale Watching Bad?
Whale watching isn't a wrong act in itself, although experts say it could be distressing for the whales. The practice has since then expanded into a multi-billion dollar business as many people dock onto boats to catch a glimpse of the majestic sea creatures.
Companies also want to give their customers the best possible experience by sometimes sticking their boats close to the whales.
Public authorities around the world have imposed restrictions on whale-watching boats to protect the whales. Some countries obligate boats to keep a distance of at least 100 meters from the whales. Some also require boats to stay next to or behind the whales at a gradual speed.
Nonetheless, scientific researches have shown that even when boats follow these restrictions, the whales are still disrupted, and the disturbance causes them to change behavior. According to Kate Sprogis, a biologist and Marie Skłowdowska-Curie Fellow at Aarhus University, whales use their sense of hearing more than they do of sight. Because of this, even if they don't see the boats, it doesn't mean that their sounds don't bother them.
In a new study, a research team from Aarhus University in Denmark believe that some boat engines are just too loud for the whales. The researchers now urge authorities to place noise emission standards on the clamor stressing the whales.
Peace and Quiet for the Whales
Other studies say that whales may face long-term effects when dealing with these disturbances. For instance, when whale mothers spend much of their energy negatively responding to underwater noise, it leaves them with little to no power to do other things. Experts say it could affect their ability to feed their offspring, deter predators and unwanted males, and to migrate to their feeding grounds.
In addition, Spogis says that because of the disturbances, whale calves might not be able to nurse properly. The researchers deduced that the noise level from a boat's engine should stay below 150 decibels. In this way, it would be possible to avoid impacting the whales' behavior.
Finally, the researchers prescribe their noise emission standard, to ensure that loud boats do not disturb whales needlessly. They also acknowledge that several whale-watching boats are already quiet, thus, complying with the proposal.
