Mass dolphin stranding linked to navy exercises

NEW SCIENTIST
June 17th, 2009 in Breaking News

An investigation into the UK’s largest ever mass stranding of common dolphins has identified military activity as the most probable cause – although no single activity can be definitively linked to the stranding.

Twenty-six common dolphins died after becoming stranded in the Fal Estuary in Cornwall, southwest England on 9 June, 2008, while a similar number were refloated by volunteers. An investigation into the cause of their deaths (pdf format) by Paul Jepson at the Zoological Society of London and his colleagues has ruled out a lengthy list of possible causes:

• Infectious disease

• Pollution

• Decompression sickness

• Attack by killer whales or bottlenose dolphins

• High-intensity acoustic inputs from seismic airgun arrays or natural sources

However, documents obtained under the UK Freedom of Information act have provided researchers with unprecedented access to military records of navy activity in the area. While there is no evidence of physical injury to the dolphins caused by sonar, “what we are left with is a mass stranding and a naval exercise – we have ruled out pretty much everything else,” Jepson says.

The UK navy had been conducting exercises in the area several days before the stranding, and on the morning of the stranding itself. Jepson suspects that these may have driven the dolphins closer to shore than normal, and that something then caused them to panic and beach.