How Noise Pollution Impacts Dolphins' Lives

Dolphins are highly intelligent creatures that rely on sound to communicate, socialise, hunt and navigate. However, human activities such as shipping, drilling, fishing and construction have led to a significant increase in underwater noise pollution, threatening dolphin populations and their way of life. Studies have shown that dolphins struggle to hear each other and cooperate in noisy environments, and the constant din can even cause hearing loss or death. With noise levels continuing to rise, it is essential to address this issue and find ways to reduce underwater noise pollution to protect dolphin populations and the marine environment they call home.

Dolphins have to 'shout' to communicate

Dolphins are highly intelligent creatures that rely on sound to communicate, socialise, navigate and hunt. However, human activities such as shipping, drilling, fishing, military sonar, and tourism have led to a significant increase in underwater noise pollution, making it increasingly challenging for dolphins to communicate effectively.

Dolphins use a variety of sounds, including whistles and echolocation, to interact with each other and their environment. Sound travels faster and farther underwater than light, making it an essential tool for dolphins to navigate their surroundings. Unfortunately, the rising levels of noise pollution are interfering with their natural communication methods.

Research has shown that dolphins have to 'shout' to hear each other over the noise. In a study conducted by the University of Bristol, researchers observed that dolphins increased the volume and length of their calls when exposed to higher levels of noise pollution. They also adjusted their body positioning, facing each other and moving closer together, to improve their chances of successful communication. Despite these adaptations, the dolphins still struggled to cooperate effectively, with their success rate in cooperative tasks decreasing significantly as noise levels rose.

The impact of noise pollution on dolphins is not just a matter of inconvenience; it can have detrimental effects on their health and survival. Dolphins rely on sound to locate prey and navigate their environment. When their ability to communicate is hindered, they may miss out on foraging opportunities, leading to a decline in their health and nutrition. Additionally, loud noises can startle dolphins, causing them to dive quickly and putting them at risk of exhaustion and decompression sickness.

The issue of noise pollution affecting dolphins is not limited to a specific location. In Hong Kong, for example, dolphin populations have declined by over 80% in 15 years due to "severe human disturbance," according to the WWF. The constant din of freight ships, ferries, and coastal development has disrupted the dolphins' natural behaviour and caused a significant drop in their numbers. Similar concerns have been raised in other parts of the world, highlighting the global nature of this problem.

Addressing noise pollution is crucial for the well-being and survival of dolphins. While some regulatory actions and noise management practices have been proposed, such as construction bans in dolphin habitats and speed limits for vessels, more comprehensive measures are needed to mitigate the impact of human activities on these fascinating creatures.

Noise pollution impacts dolphins' ability to cooperate

Dolphins are highly intelligent and social animals that rely on sound to communicate, socialise, hunt, navigate, and reproduce. However, noise pollution from human activities such as shipping, drilling, construction, and military sonar is increasingly threatening their ability to cooperate and survive.

Dolphins use a complex range of sounds, including whistles and echolocation, to coordinate their behaviour and work together. They are known to increase the volume and length of their calls or the frequency to compensate for noise pollution. For example, a study conducted by researchers from the University of Bristol, UK, found that when exposed to increasing levels of noise, dolphins nearly doubled the loudness and duration of their whistles and adjusted their body positioning to face each other.

Despite their efforts to adapt, noise pollution still significantly impacts the ability of dolphins to cooperate. In the Bristol University study, the success rate of two bottlenose dolphins, Delta and Reese, in a cooperative task dropped from 85% during ambient noise control trials to only 62.5% when exposed to very high noise levels. This finding highlights the detrimental effects of noise pollution on the ability of dolphins to work together.

The negative consequences of noise pollution on dolphin cooperation can have far-reaching implications for their health and survival. If dolphins struggle to cooperate in foraging, it can negatively impact their individual health and, consequently, the health of the entire population. Additionally, noise pollution can disrupt their echolocation abilities, which they rely on to find food, socialise, and navigate underwater.

The growing body of research on this topic underscores the urgency of addressing noise pollution to protect dolphin populations and the wider marine environment. Some measures to reduce underwater noise pollution include regulations, speed limits for vessels, route alterations, and the development of noise-reducing technologies.

Human activity is a major cause of underwater noise

Shipping isn't the only culprit, though. Drilling for projects like offshore wind farms, military sonar, and tourism also play a role in creating underwater noise pollution. All of these activities can have detrimental effects on dolphins, who rely on sound to communicate, navigate, and find food.

Dolphins use echolocation and whistles to work together for hunting and reproducing. When exposed to high levels of human-created noise, they struggle to hear each other and cooperate. In a study conducted by the University of Bristol, researchers found that dolphins had to increase the volume and length of their calls when noise pollution rose. They also adjusted their body positioning to face each other and moved closer together, likely to separate the signal of their partner from the polluting noise.

Despite these adjustments, the dolphins' success rate in cooperative tasks dropped significantly when exposed to very high noise pollution. This could have negative consequences for their health and population numbers. As Pernille Mayer Sørenson, a PhD candidate at Bristol University, explained, "If you are exposed to noise and that prevents you from communicating with your friends when you are foraging together, that might lead to missed opportunities and could have an impact on your individual health if that's a certain behaviour that is essential to your survival."

The problem of human-caused underwater noise pollution is not limited to a single location. For example, in Hong Kong, a highly urbanized and industrialized region, dolphin populations have dropped by over 80% in 15 years due to "severe human disturbance," according to the WWF. The construction of the Hong Kong-Zhuhai-Macau Bridge, the longest sea crossing in the world, and other ongoing development projects are contributing to the noise pollution in the area.

While some countries, such as Germany, have implemented noise limits for offshore construction, more needs to be done to address this issue. As Richard Sabin, the Principal Curator of Mammals at the Natural History Museum, states, "To preserve the acoustic world that many marine organisms rely on, we need to have the same focus on noise pollution as we do on climate change."

Noise pollution can cause hearing loss or death

Dolphins are highly intelligent and sensitive creatures that rely on sound to navigate, communicate, hunt, and socialise. However, their acoustic world is under threat from human-made underwater noise pollution, which has been increasing in recent decades. Noise pollution can cause hearing loss or even death in dolphins, as well as a range of other harmful effects.

The sources of underwater noise pollution include shipping, drilling for projects like offshore wind farms, fishing vessels, military sonar, and tourism. The European Commission found that underwater background noise levels have doubled every decade in the last 60 years, mainly due to shipping. This has severe implications for dolphins, who rely on sound to navigate and communicate.

Research has shown that dolphins struggle to hear each other and cooperate in noisy environments. In one study, dolphins had to work together to press underwater buttons within one second of each other. When exposed to increasing levels of noise pollution, the dolphins increased the volume and length of their calls, and also adjusted their body positioning to face each other. Despite these efforts, their success rate in the cooperative task dropped significantly.

Noise pollution can also disrupt echolocation, a sensory ability that dolphins use to find food, socialise, and navigate underwater. In extreme cases, it can cause physical harm, including temporary hearing loss. The World Wide Fund (WWF) has reported that dolphin populations in Hong Kong have declined by over 80% in 15 years due to "severe human disturbance".

The impact of noise pollution on dolphins is not limited to hearing loss or communication difficulties. Loud noises can scare dolphins, causing them to dive quickly and putting them at risk of exhaustion and decompression sickness. This can be life-threatening, as seen in cases of whale strandings and deaths linked to the use of very loud devices such as anti-submarine sonar and seismic guns.

To protect dolphins and other marine life, it is crucial to address the issue of noise pollution. Some measures to reduce underwater noise pollution include regulations, speed limits for vessels, route alterations, and the development of noise-reducing technologies.

Oil spills and chemical pollution also affect dolphins

Oil spills can contaminate the water and the prey that dolphins eat. When dolphins swim through oil slicks, there is a risk of toxic oil entering their blowholes and mouths, and they can inhale volatile toxic chemicals. Additionally, oil spills can kill off smaller animals, such as krill, that are a food source for dolphins.

Chemical pollution, such as the release of dangerous man-made chemicals like PCBs (Polychlorinated Biphenyls), can also have detrimental effects on dolphins. PCBs build up in the food chain, with the highest amounts found in top predators like dolphins. These chemicals cause sterility and are decimating dolphin populations.

The impact of oil spills and chemical pollution on dolphins underscores the importance of addressing these environmental threats to protect dolphin populations and their habitats.

Frequently asked questions