Baraza

Category: Amazing facts | Date: Dec 01 2008 | By: baraza

It has happened again and nobody knows why. Conservationists are mourning the deaths of over 150 pilot whales that  beached themselves in Tasmania, many of them were injured after being battered against rocks. Thirty were shepherded back to the sea by rescuers. It is thought that they became stranded on their annual migration to and from arctic waters. I was especially touched to hear that stranded whales were calling to those whales still out at sea.Scientists and rescuers think that this was a warning to their friends and family.

For amazing but sad photos of this incident check out the gallery here here and news stories on VOA here and CBS News here. Bloggers are also reporting the incident but only one blogger, on Live Science has proposed an explanation

He says “The Deafwhale Society is doubtful that these 11 animals are safe and sound. The whales are moving with the current that normally flows from west to east in the Bass Strait. We predict two outcomes: (1) The earthquake-injured whales will end up in the bellies of hungry sharks, and (2) if the sharks don’t culled them, there is a good chance they will strand again somewhere near Flinder’s or Cape Barren Islands. If they get passed the shallow water between Flinder’s and Cape Barren, they will likely be washed out into the Tasman Sea.

The SEAQUAKE SOLUTION (http://deafwhale.com) developed by the Deafwhale Society indicates that most whale mass strandings are caused by undersea earthquakes. More specifically, the stranding on 20 November 2008 on Anthony’s Beach near Stanley was caused by the event listed below:

Source: US Geological Service
FILE CREATED: Sun Nov 23 05:21:55 2008
Circle Search Earthquakes= 1
Circle Center Point Latitude: 45.000S Longitude: 100.000E
Radius: 1000.000 km
Catalog Used: PDE
Data Selection: Preliminary Data Only

CAT YEAR MO DA ORIG TIME LAT LONG DEPTH MAGNITUDE
PDE-Q 2008 10 25   223507.93 45.22S  97.05E 10 km 5.1 mbGS

Local time at the epicenter was 6:35 am on 26 October 2008. The depth of focus of the 5.1 magnitude earthquake was restrained by the computer at less than 10 km.

In general, the seafloor danced rapidly during the earthquake, pushing and pulling at the water in a fashion to generate excessive changes in the hydrostatic pressure surrounding the area where the pod of pilot whales were feeding. The quick fluctuations in pressure caused the volume of air inside the head sinuses of the whales to increase and decrease rapidly in response to the changing pressure resulting in a barotraumatic injury in the membranes that surround these sinuses.

The whales use these sinuses to generate echonavigation signals and to read the returning echo, thus an injury of this nature would not only disrupt diving and feeding but also disable echonavigation. A pod of earthquake-injured pilot whales would surface but not be able to dive again, nor be able to generate or determine direction of their navigating signals.

The vibration from the earthquake would be like a dinner bell to any nearby sharks.

The pod would huddle together to fight off shark attack. The sharks would take the most seriously injured. The rest would stay huddled swimming off in an unknown direction in an attempt to move away from the sharks.

Any swimming action by the pod would turn their streamline bodies downstream in the path of least resistance. Surface currents from the epicenter, known as the Antarctic Circumpolar Current, flow from the west to the east and would direct the wounded pod A

An interesting theory but I’m not 100% convinced. Nobody can prove that there were sharks in the area.  I don’t doubt that a quake could simply confuse the sharks…. but this does not explain why these whales seem to beach themselves frequently on the Tasmania shores.

According to the CBS News  article only one week ago rescuers saved another 11 pilot whales among more than 60 stranded on a beach in northwestern Tasmania, which is an island.

I wonder if anyone has investigated whether these previous strandings were also linked to sea quakes.

It’s Worlds AIDS day, stay safe.

Tags: Pilot whales, sharks, Tasmania, whale stranding

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