Pilots Need Navigators in Tasmania

Stranded pilot whales off King Island, Tasmania

This past weekend Tasmania’s King Island was the scene of a very large stranding of pilot whales, some 200, and seven bottlenose dolphin. Despite the efforts of local authorities and many volunteers leading bucket brigades and watches on the stranded animals, just forty-eight pilots and five bottlenose made it back into the water.

Apparently Tasmania is a hotspot for whale strandings in Australia and nearly eighty-percent of strandings occur on its coastlines. Just last month forty-eight sperm whales were lost when they stranded on a sandbar in the same relative region. This “hotspot” identity of course makes me very curious. Is there something about the geography of the region or some underwater disturbance that drives stranding behavior in several species of whale? Is there something about typical whale and dolphin behavior in the area that creates these massive strandings? Is there some deep water ridge with prevailing currents that brings them up to the surface too fast? Wait… can dolphins and whales actually get “bent” in the same sense that a human diver can?

While many marine mammals shunt blood towards the heart and lungs and other key organs during deep dives – and away from secondary systems like the limbs – I’m not sure if they show some of the same predisposition to dissolved gas tomfoolery that people do. Of course the whales aren’t using SCUBA, they’re holding one long breath. But it still makes me wonder. Even if you have just a single volume of gas in your lungs, if you’re deep enough down and the pressure constricts it, is there a danger in surfacing too fast? Ideas, anyone?

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3 Comments to “Pilots Need Navigators in Tasmania”

  1. I’ve been reading along for a while now. I just wanted to drop you a comment to say keep up the good work.

  2. Whales have been shown to get bent on a regular basis. Scientists have found pits in their joints similar to those found in humans who have had excessive exposure to decompression sickness related to deep water technical diving.

  3. This is an area of rather intense study, thanks to a few strandings of deep-diving beaked whales during naval sonar training missions. The US Navy and others are funding research to better understand both the dive profiles of whales, and the physiological changes that may occur, some of which seem to mimic the bends. Interestingly, it is not necessarily just surfacing too quickly that can perhaps cause nitrogen build-up; one current theory is that beaked whales may enter a series of shallow dives, fleeing sonar signals that they perhaps mistake for orcas (or, the sonar sounds are simply really obnoxious and freak them out), and that these shallow dives interrupt can gradually build up nitrogen levels to a harmful point.

    As the previous commenter noted, research out of Woods Hole a few years back found that older sperm whales have bone damage that resembles that found in humans after suffering the bends. it may be that whales routinely have some “bad” experiences with nitrogen damage in the course of their lives.

    I would doubt that underwater topography would cause whales to surface too quickly (eg Tasmania). That area has indeed long been a place where whales come ashore; one idea is that the offshore slope there is so gradual that it is not easily perceived as a shoreline via echolocation (I saw a paper on this a few years back, but can’t say for sure it applies in the exact site of the recent stranding)

    See the Acoustic Ecology website for ongoing coverage of ocean noise issues, and other noise-related environmental topics. http://AEInews.org http://AcousticEcology.org