Whale stranding, also known as beaching, occurs when whales leave the ocean and end up on land, typically on a beach. While some strandings are natural events, human activities increasingly influence their occurrence. Beached whales often face death due to a combination of factors, including the physical consequences of being out of water.
Biological and Environmental Drivers of Stranding
Natural factors contribute significantly to whale strandings, often involving navigational errors. Whales rely on sophisticated systems like echolocation and the Earth’s magnetic field for navigation. Gently sloping coastlines or sandy beaches can interfere with echolocation signals, leading whales to misjudge water depth and inadvertently swim ashore. Disturbances in the Earth’s geomagnetic field can also confuse whales, causing navigational mistakes.
Illness, old age, or injury can weaken whales, making them disoriented or too frail to navigate effectively, increasing their vulnerability to stranding. Severe weather events, strong currents, or unusual tidal patterns may push whales towards shore. The social dynamics of some whale species can also lead to mass strandings; if a sick or disoriented leader of a pod heads towards shore, others may follow due to strong social bonds. This “follow-the-leader” behavior is noted in highly social species like pilot whales.
Human-Related Contributions to Stranding
Human activities play a role in whale strandings, with underwater noise pollution being a significant concern. Naval sonar can disorient whales, causing them to surface too quickly or flee into shallow waters. This rapid ascent can lead to decompression sickness, similar to “the bends” in human divers, where nitrogen bubbles form in their blood and organs. Seismic surveys also produce intense underwater noise, affecting whale behavior and navigation.
Entanglement in fishing gear poses another threat, as nets and lines can restrict a whale’s movement, causing injury, exhaustion, or drowning, making them susceptible to stranding. Ship strikes can cause severe injuries or death, with struck whales often washing ashore. These collisions can result in blunt force trauma, leading to internal bruising, hemorrhage, and broken bones. Marine pollution can sicken whales, impairing their ability to survive or navigate effectively.
Physiological Consequences of Landed Whales
Once on land, whales face severe physiological challenges that quickly lead to death. The immense body weight of a whale, normally supported by water’s buoyancy, crushes its internal organs, lungs, and blood vessels when subjected to gravity. This pressure can cause fatal organ failure even if the whale is returned to the water. Overheating, or hyperthermia, is another serious issue because whales possess a thick layer of insulating blubber, which traps heat on land. Without the cooling effect of water, their body temperature rises rapidly.
Dehydration also contributes to their demise, as whales are adapted to absorb water from their marine environment and food, not to drink fresh water. Rapid water evaporation from their lungs further exacerbates dehydration. Whales also experience extreme stress and shock when stranded. Their blowholes can become blocked, or their respiratory muscles may fail under the pressure of their own weight, leading to suffocation. The combination of these factors leads to a rapid deterioration of the whale’s condition, with many unable to survive beyond a few hours once beached.