Whale stranding occurs when whales and other marine mammals become stuck on land, often resulting in their death. These events capture public attention. While whales are powerful inhabitants of the ocean, their presence on shore highlights a complex issue. Understanding why these majestic creatures end up stranded is an important focus for scientists and conservationists. It requires examining various contributing factors, both natural and human-induced.
Natural Factors Behind Strandings
Whales can become stranded due to various natural factors that compromise their ability to navigate or survive in their marine environment. One common reason involves the health of individual animals. Whales suffering from infections, parasitic infestations, or chronic illnesses often become weakened and disoriented, making them susceptible to drifting into shallow coastal areas. Similarly, whales that are very old or very young may lack the strength or experience to swim effectively against strong currents or navigate complex underwater topographies. Severe injuries, perhaps from natural predators like orcas, can also incapacitate a whale, leading it to seek refuge in shallower waters or become too weak to avoid stranding.
Navigation errors present another natural cause for beachings. Whales depend on sophisticated internal systems, including echolocation and sensitivity to Earth’s magnetic fields, for their long-distance journeys. Unusual coastal shapes or sudden, gently sloping changes in seafloor topography can interfere with their echolocation signals, leading them to misjudge water depth and become trapped. Furthermore, geomagnetic anomalies, which are localized disturbances in the Earth’s magnetic field, can confuse a whale’s magnetic sense, causing it to deviate from its intended path and potentially head towards shore.
Environmental conditions also play a role in natural strandings. Intense storms, powerful ocean currents, or unusually high tides can physically push whales into dangerous coastal zones from which they cannot escape. Reduced visibility in stormy or murky waters can further impair their navigational abilities, increasing the risk of disorientation. Additionally, whales may follow their prey, such as schooling fish or squid, into unfamiliar or shallow waters, especially during feeding events. If the tide recedes quickly or the whales become disoriented while pursuing food, they can become trapped on the receding shoreline.
Human Activities Contributing to Beachings
Human activities significantly contribute to whale strandings by disrupting marine environments and directly harming cetaceans. Underwater noise pollution is a prominent concern. Sounds from commercial shipping, seismic surveys for oil and gas exploration, and military sonar can disorient whales, interfering with their communication and echolocation systems. Mid-frequency active sonar, often used by navies, has been linked to mass strandings of deep-diving species like beaked whales, potentially causing them to surface too quickly, leading to decompression sickness or fleeing towards shore.
Entanglement in fishing gear poses another substantial threat. Whales can become caught in nets, lines, and traps, which can restrict their movement, cause severe injuries, or lead to exhaustion and drowning. These incapacitated animals may then be swept ashore by currents or become too weak to navigate away from the coastline. The increasing number of fishing operations globally escalates the risk of such interactions, impacting various whale species.
Collisions with vessels, known as ship strikes, are also a direct human cause of whale mortality and stranding. Large ships can inflict severe injuries or instant death upon whales, particularly in busy shipping lanes. Carcasses of whales killed by ship strikes may then wash ashore, appearing as stranding events. The expansion of maritime traffic worldwide increases the likelihood of these fatal encounters.
Chemical pollution and toxins further compromise whale health. Industrial runoff, agricultural chemicals, and microplastics accumulate in the marine food chain, leading to bioaccumulation of harmful substances in whales. This can weaken their immune systems, impair neurological functions, and make them more vulnerable to disease or disorientation, indirectly leading to stranding. Additionally, human development along coastlines can degrade critical whale habitats, altering natural patterns and increasing the chances of whales encountering hazardous shallow areas.
The Interplay of Multiple Causes
Whale strandings are rarely attributed to a single isolated event, but rather emerge from a complex interplay of various factors. Often, a combination of natural vulnerabilities and human-induced pressures creates a cumulative effect, leading to a stranding. A whale already weakened by disease or old age, a natural factor, may become more susceptible to disorientation caused by underwater noise pollution from human activities. This compounding stress can push an already compromised animal past its limits.
Consider a scenario where a pod of whales is navigating an unfamiliar coastline, perhaps disoriented by unusual currents or geomagnetic anomalies. If, at the same time, they encounter loud military sonar, the combined stressors can overwhelm their navigational systems, driving them towards shore. Climate change also adds another layer of complexity, altering prey distribution and increasing the frequency of extreme weather events, which can exacerbate existing vulnerabilities. Researchers face significant challenges in determining the precise cause of a stranding, as it often requires comprehensive necropsies and environmental assessments to unravel these intertwined influences.
Research and Conservation Efforts
Understanding and addressing whale strandings is a global priority, leading to various research and conservation initiatives. Scientific research, including detailed necropsies of stranded whales, provides invaluable data on their health, diet, and exposure to environmental stressors. This post-mortem examination helps identify specific causes of death and potential links to broader ecosystem health. Continuous monitoring programs, like the Scottish Marine Animal Stranding Scheme (SMASS), collect long-term data to track stranding patterns and identify emerging threats.
Response and rescue teams play a direct role in assisting live stranded whales. Trained marine mammal experts and volunteers work to stabilize animals, provide medical assessment, and, when feasible, guide them back to deeper waters. Beyond immediate rescue, conservation efforts focus on mitigating human impacts. This includes developing quieter shipping technologies, implementing stricter regulations on underwater noise, and designing fishing gear to reduce the risk of entanglement. Raising public awareness about reporting strandings and supporting marine conservation initiatives also contributes significantly to protecting these vulnerable marine mammals.