Whale Stranding: Five Questions Answered



The death of some 200 pilot whales on a Tasmanian beach has renewed doubts about what causes such mass stranding and whether they can be prevented.

With the help of Karen Stockin, a whale-stranding expert at Massey University in New Zealand, here are the answers to five key questions:

What causes mass stranding?

Scientists are still trying to solve it. They know that there are different types of stranding events, with different explanations that can overlap. The causes can be natural, based on bathymetry, the shape of the ocean floor, or they can be species-specific.

Pilot whales and several smaller dolphin species are known to beach regularly, especially in the Southern Hemisphere, according to Stockin. In some cases, a sick whale headed for the shore and a whole group followed them unknowingly.

Does it happen in certain areas?

There are some global hotspots. In the Southern Hemisphere, Tasmania and New Zealand’s Golden Bay have seen several cases, and in the Northern Hemisphere, Cape Cod Bay, Massachusetts, United States is another hotspot.

In those areas there are similarities between the topography of the beaches and the environmental conditions. For example, Cape Cod and Golden Bay share a prominent narrow coastal land feature and shallow waters with large tidal variations. Some people refer to these areas as “whale traps” because of the speed at which the tide can recede.

Are strandings becoming more common?

Possibly. Strandings are natural phenomena and have been documented since the time of Aristotle. The health of the oceans, however, has deteriorated in recent decades.

Beaching could become more common as human use of the seas, shipping traffic and chemical pollution increases.

Epizootic diseases, outbreaks of diseases affecting a specific animal species, could also lead to more. But there is still a lot to understand about the phenomenon, Stockin said.

Is climate change a factor?

Research into how climate change is affecting marine mammals is still in its infancy. Experts know that climate change can result in changes in the distribution of prey and predators. For some species, this could lead the whales to come closer to shore.

For example, recent research based on current climate prediction models suggests that the distribution of sperm whales and blue whales in New Zealand could vary considerably by 2050.

Can stranding be prevented?

Not really. Since strandings occur for a multitude of reasons, there is no one-size-fits-all solution. But Stockin said by better understanding if and how human-induced changes are causing more mass stranding, solutions can be found.