[back] Whale and Dolphin killing

Dolphin deaths: was sonar to blame?

The Royal Navy was to blame. Or killer whales. Or something else, as yet unknown.

More than 48 hours after 26 dolphins died near Falmouth in Cornwall, no one can really say for certain what caused the biggest mass dolphin beaching seen in Britain for decades.

Tests on the dead dolphins have shown very few had food in their stomachs, meaning they were unlikely to have become stranded in the Percuil river while chasing a shoal of fish.

Thus, the British Divers Marine Life Rescue believes they were probably "scared ashore".

The most eye-catching idea is that the pod was frightened by a killer whale - less notable for the understandable notion that a killer whale could cause panic as for the revelation (to me at least) that these giant predators are "surprisingly common" in UK waters, even the English Channel.

But the focus is also on the navy, which was carrying out exercises off Cornwall before the beachings. The speculation is that explosions or sonar could have frightened and disoriented the pod.

This line is all over today's papers, but there are some dissenting voices - not least the navy itself, which insists it did not use any live ammunition for some time before the incident.

Technology website the Register notes that while so-called low-frequency sonar, a relatively new piece of naval equipment which allows quiet, modern ships and submarines to be detected at long range, has been linked with previous dolphin and whale strandings, the navy wasn't using this in its exercises.

Instead, short-range "sidescan" sonar was being used, something, the site notes, that has been "widely used worldwide for decades, and not just by navies".

It adds:

The idea that low-frequency active [sonar] has something to do with strandings in general is at least believable - the idea that sidescan lay behind this incident is ridiculous...

And seriously, UK media people, with all your sonar-kills-dolphins headlines this week. It would be a good idea to pull your head out of the dark for a look round once in a while.

Of course, the navy could always be misinforming us over the type of sonar used, but it seems equally likely something else is behind the incident.

In the past, wholesale beachings of dolphins have been put down to another possible reason - mass suicide. Unlikely? It is, apparently, behaviour previously observed in the wild.

12.45pm update:

It seems suicide is being considered in the Cornish case, too, according to a new story by the Guardian's Steven Morris.