The deaths of around 200 pilot whales beached in Tasmania have again raised questions about what causes such mass strandings and whether they can be prevented.
With the help of Karen Stockin, a cetacean stranding expert at New Zealand’s Massey University, here are the answers to five key questions:
What causes mass strandings?
Scientists are still trying to figure it out. They know that there are several types of stranded events, with several overlapping explanations. The causes can be natural, based on bathymetry – the shape of the ocean floor – or they can be species-specific.
According to Stockin, pilot whales and several smaller species of dolphins are known to massage themselves regularly, especially in the southern hemisphere. In some cases, a sick whale headed for shore, and the whole group unknowingly followed them.
Does it happen in certain areas?
There are several global hotspots. In the Southern Hemisphere, Tasmania and New Zealand’s Golden Bay have seen a few cases, and in the Northern Hemisphere, the United States’ Cape Cod Bay, Massachusetts, is another hot spot.
In these areas there are similarities between beach topography and environmental conditions. For example, Cape Cod and Golden Bay share a prominent narrow coastal landmass and shallow water with large tidal variations. Some people call such areas “whale traps” because of the speed at which the tide can recede.
Are strandings more common?
Possibly. Stranded natural phenomena have been documented since the days of Aristotle. However, the ocean’s health has deteriorated in recent decades.
Strandings may become more common as human use of the sea, shipping traffic and chemical pollution increase.
Epizootic diseases – disease outbreaks affecting a particular animal species – can also lead to more. But there is still much to understand about the phenomenon, Stockin said.
Is climate change a factor?
Research into how climate change affects marine mammals is still in its infancy. Experts know that climate change can lead to changes in the distribution of prey and predators. For some species, this can lead to whales coming closer to shore.
For example, recent research based on current climate prediction models suggests that by 2050 the distribution of sperm whales and blue whales in New Zealand could vary significantly.
Can stranding be prevented?
Not really. As stranding occurs for a multitude of reasons, there is no one-size-fits-all solution. But Stockin said that by better understanding whether and how human-induced changes are causing more mass strandings, solutions may be found.