Of Whales and Quakes

The recent strandings of whales in Golden Bay had me thinking about possible causes.

These seemingly random events mystify humans and, if you’ve ever had the misfortune to witness one, they are a dreadful thing to behold. Down on the beach will be huge creatures thrashing about, sometimes mewling in agony, while DOC staff and volunteers try to ease their discomfort and keep them alive until they can be coaxed out to sea at the next high tide.

The only time I have witnessed a stranding first-hand was when 59 sperm whales beached themselves at Wainui Beach north of Gisborne on the 18th of March 1970. At the time it was something of a spectacle and, as a youngster, I was taken along to have a look. It was a scene of pure horror down amongst the huge creatures, and I was unfortunate enough to witness the attempted removal of a jawbone by someone with a chainsaw. Not something I enjoyed.

Nowadays we take a slightly more humane view of such things, and the people on the beach are more likely to be trying to save the creatures than poke them with sticks and mutilate them as if at a macabre sideshow.

Unfortunately for the sperm whales at Wainui Beach, our skills at coaxing and refloating were not well-developed. They died and had to be hauled away to a huge grave bulldozed into the sandhills. I haven’t been back there for many a year, but we were warned at the time not to cross the barriers and go walking on top of the grave. With such large carcasses, cavities containing noxious remnants would develop over time, and it would be dangerous to come in contact with the material through a cave-in.

Mass strandings of whales are not too uncommon around New Zealand coasts, by which I mean they happen every few years, sometimes in clusters. Speculation as to the cause of such strandings has ranged widely. Some have suggested simple navigational error by the leader, with the rest of the pod loyally following the lead, even to the extent of re-beaching themselves after being coaxed out to sea. Others have suggested that illness or disease causes various members of the pod to accidentally or purposely beach themselves, leaving the healthy members of the pod leaderless and at a loss as to what to do except follow their leaders. Still others have speculated that storms, thunderstorms or other natural phenomena upset the whales’ navigational skills, and that the beaching is simply a result of being off-course.

Today, it is still largely a mystery as to why the initial strandings occur, and much uncertainty surrounds the reason for some or all of the refloated creatures returning to strand themselves again, only to die with their comrades.

It is now well-known that gravitational and magnetic anomalies are associated with the ground deformation that occurs as part of our tectonic processes. As the Earth’s tectonic plates move, strain builds up in various areas as rock is compressed or stretched over time before it eventually ruptures, and we feel an earthquake. During the process land can rise or fall, rock is gradually tilted, and magnetic and gravitational fields are altered slightly.

Nowadays, our seismologists and geologists regularly prepare magnetic and gravitational anomaly maps as they study the changing strain around New Zealand. Prior to the two earthquakes near Farewell Spit on the 16th and 17th of January, I was wondering what the tectonic stress build-up was like in the vicinity. The sites of the three recent strandings are in Golden Bay near the earthquakes’ epicentres.

Linking the strandings with tectonic deformation is drawing a very long bow, but is something that should be considered, nevertheless. It’s not uncommon for strandings to occur near Farewell Spit, but the sandspit has been there for some time. It seems unlikely that creatures with such well-developed migratory habits would have neglected to take the sandbar into account.

However, if whales rely on magnetic fields for their migration (as some birds have been shown to do) then a local anomaly due to tectonic strain in Golden Bay could easily bring their course a few kilometres south along the spit to Puponga where so many of them beached.

I wonder if anyone is studying this possible link. Perhaps they’d like to post some information about their work.

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