Mass death of pilot whales on the Isle of Lewis, United Kingdom

Problems

• Mass stranding of pilot whales

  On July 16, 2023, a tragic event occurred on the Isle of Lewis, a northwestern Scottish island. A pod of 55 pilot whales was found stranded on a beach near the village of North Tolsta. Most of the whales died shortly after washing up, and only one whale survived after being refloated by rescuers. The rest were euthanized on welfare grounds, as the shallow beach and rough wave conditions made it too unsafe to attempt further rescue operations. This was the worst mass whale stranding in Scotland for decades and raised questions about the causes and consequences of such incidents.
  
  Pilot whales are small whales that belong to the dolphin family. They are highly social and intelligent animals, forming strong bonds with their pod members. They live in deep waters and feed mainly on squid and fish. They use echolocation to navigate and communicate in their dark and vast habitat.
  
  Sometimes, pilot whales get into trouble when they venture too close to shore. They may follow prey, avoid predators, or respond to environmental cues that lead them astray. They may also strand due to illness, injury, or human interference, such as noise pollution or fishing gear. When one whale gets into difficulty and strands, the rest of the pod may follow out of loyalty or confusion, resulting in a mass stranding.
  
  The exact cause of the stranding on the Isle of Lewis is still unknown, but experts suspect it may have been triggered by a female giving birth. One of the dead whales appeared to have had a vaginal prolapse, which could have caused distress and disorientation to the whole pod. Other factors, weather, tides, or topography, may have also influenced the stranding.
  
  Another cause of the stranding of the whales can be attributed to underwater noise from the military's use of sonar – using sound waves to see in the water. A study published in the journal PNAS last year showed that multiple whale species slowed or halted foraging behaviours when they heard naval sonar or predator sounds.
  
  The stranding was reported at around 07:00 on Sunday morning by a resident who spotted the whales on Traigh Mhor Beach. The British Divers Marine Life Rescue (BDMLR), a marine charity specializing in responding to stranded marine animals, was alerted and mobilized a team of volunteers and experts to the scene. They were joined by other agencies and organizations, such as the Coastguard, Fire and Rescue, Scottish Marine Animal Stranding Scheme (SMASS), Scottish SPCA, Civil Air Support, and local vets.
  
  The rescuers found that most of the 55 whales had already died at night, as they could not survive for more than six hours out of water. They tried to give first aid to the 15 surviving whales, which included eight adults and four calves. They managed to refloat one of the more active whales, but it stranded again further down the beach and later died. 
  
  The remaining whales suffered from dehydration, exhaustion, and internal damage caused by their weight crushing their organs. After assessing the situation and consulting with vets, the rescuers euthanised the whales on humanitarian grounds at around 15:30.
  
  The stranding on the Isle of Lewis devastated the pilot whale population and the local community. Pilot whales are not endangered but face various threats from human activities, such as overfishing, climate change, pollution, and ship strikes. Mass strandings can have significant impacts on their genetic diversity and social structure, as well as their ecological role as predators.
  
  The stranding also affected the people who witnessed and responded to it. Many were shocked and saddened by seeing dead or dying animals on their shore. Some were traumatized by having to euthanize or dispose of the carcasses. Others were inspired by the courage and compassion of the rescuers who tried to save them.
  
  The stranding also raised awareness and curiosity about pilot whales and their behavior. SMASS will conduct post-mortem examinations of the bodies to determine their health status and possible causes of stranding