Killer whale population at serious risk

The number of killer whales could be halved in a few decades due to pollutants in the seas, according to new research.

Steps to ban chemicals – known as polychlorinated biphenyls (PCBS) – were first made 40 years ago, but they remain a deadly threat to the mammals at the top of the food chain.

A new study, involving researchers at the University of St Andrews, shows that current concentrations could severely deplete populations of killer whales in the most heavily contaminated areas within 30 to 50 years.

Professor Ailsa Hall, director of the Sea Mammal Research Unit, said: “In these contaminated areas, we rarely observe newborn killer whales.” Orcas are among the mammals with the highest level of PCBS in their blubber, with values as high as 1,300 milligrams per kilogram.

Animals with levels as low as 50mg per kg can show signs of infertility and immunity problems. Researchers from St Andrews and Aarhus University in Denmark found the number of killer whales could rapidly decline in 10 of their 19 populations.

They are particularly threatened in heavily contaminated areas near Brazil, the Strait of Gibraltar and the west coast of the UK.

The east coast of Greenland is also affected due to high consumption of seals who consumer PCBS.