Why Do Whales Strand? Unraveling the Mystery
By Rosemary Ellis
In the vast expanse of our oceans, there remains a mysterious occurrence that continues to challenge researchers and stir global concern – cetacean strandings. Whales and dolphins often strand on shore, sometimes in very large numbers, prompting the need for a closer examination of the underlying factors contributing to these perplexing events.
Recent mass strandings have sparked worldwide attention and left many of us wondering why cetaceans strand. In July 2023, more than 50 pilot whales became stranded off the coast of Lewis, Scotland. Only one whale survived after being successfully released. A week later, nearly 100 pilot whales met a similar fate – all of them either died or were euthanized – on a beach in Australia. These events, along with countless others that have occurred worldwide, serve as poignant reminders of the fragility of cetaceans and the urgent need for action.
The reasons behind cetacean strandings are far from straightforward and involve multiple complex factors. Human activities appear to play a substantial part in many of these distressing events, although the causes are often unknown.
For example, a study conducted by the National Marine Fisheries Service focused on examining the largest known mass stranding of Stejneger's beaked whales. This extensive research shed light on the potential role of seismic testing for oil (involving huge blasts into the sediment to detect returning sound waves indicating possible oil reserves) or possibly intense active military sonar use in these tragic events. Some of these intense military sonars can put out the equivalent sound of the space shuttle taking off. Seismic airguns used by the oil industry can be even louder. The study found a compelling association between seismic testing and naval active sonar exercises and an increased likelihood of strandings, indicating that the powerful sound waves emitted during these exercises can disorient and distress these enigmatic marine creatures, leading them astray.
When one considers that marine mammals depend on an acoustic environment to survive in the ocean, then it’s understandable that major sound assaults are wreaking havoc on cetaceans by interfering with their ability to communicate, locate food, navigate, detect predators and find mates. Strandings may result when animals are disoriented by loud underwater noise or startled into rising to the surface too fast, resulting in gases in the blood coming out of solution as bubbles, a painful and often lethal condition known to divers as "the bends".
In addition to active military sonar use and testing, other human-generated undersea noise includes very loud noises generated by ships and the seismic blasting employed in undersea oil and gas exploration, associated with mass strandings of whales and dolphins. The harmful effects of active sonar on whales and dolphins have been well-documented, causing pain, tissue damage of the inner ear, disorientation and distress that can lead to strandings.
Other factors, such as the health of individual whales and dolphins, also play a significant role in strandings. Older or ailing individuals may become disoriented, accidentally ending up stranded on shore. Additionally, disruptions in Earth's magnetic fields might lead to navigational errors, further contributing to these unfortunate events.
Research published in Frontiers in Marine Science delved into the intriguing influence of social behaviors within cetacean pods on strandings. These majestic beings are known for their tight-knit social bonds, and the study explored how these intricate dynamics can sometimes result in multiple individuals following a stranded pod member, even if they are not in distress themselves. The findings illuminated the interconnected nature of cetacean communities and how these social ties can inadvertently contribute to strandings in certain circumstances.
Plastic pollution, other pollutants, ship strikes, and fishing gear pose threats to marine mammals and can cause strandings, with ingestion-related or entanglement complications affecting their survival. But that may not explain mass strandings. Climate change further exacerbates the situation, impacting marine ecosystems and prey distribution, forcing cetaceans into unfamiliar and potentially hazardous waters. Unsustainable fishing practices further contribute to the depletion of marine resources and jeopardize the well-being of these creatures.
Whale strandings are just the tip of the iceberg of the damage that humans are inflicting on whales and dolphins. By understanding the intricacies of standings and their probable connections to human activities, like active sonar use, we can work towards eliminating the threats.
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