Whale strandings may not be for family reasons - study

A pilot whale stranded at Spirits Bay. Photo / Peter de Graaf

Whales that beach themselves may not be doing so for family reasons as scientists had previously thought.

A theory behind the strandings says healthy whales are drawn into shallow water trying to support family members that are sick or disoriented.

But a new DNA study of long-finned pilot whales stranded in Tasmania and New Zealand has questioned the "care-giving" model.

The study, published in the Journal of Heredity, found stranded groups were not necessarily members of one extended family.

It also found many whale calves become stranded without their mothers.

"If kinship-based social dynamics were playing a critical role in these pilot whale strandings, we would expect to find that the individuals in a stranding event are ... all related to each other," said the study's lead author, Marc Oremus from the University of Auckland.

"We would (also) expect that close relatives, especially mothers and calves, would be found in close proximity to each other."

Long-finned pilot whales are the most common species to strand en masse.
Researchers analysed DNA from 490 whales in 12 beachings, the largest involving more than 150 whales, all of which died.

The position of the whales was also mapped to find out whether animals found near each other were related.

Typically they weren't - even nursing calves and their mothers were often widely separated, while many mothers were missing altogether.

"The separation of related whales might actually be a contributing causal factor in the strandings, rather than simply a consequence," Mr Oremus said.

The research team says the study has implications for rescue efforts of beached whales.
They have cautioned against attempting to refloat calves with the nearest mature female under the assumption that it is the younger whale's mother.