About 55 whales were stranded on Long Beach, Kommetjie with adults and calves coming ashore in bad weather from 5.30am.
Veteran marine conservationist Nan Rice, who chairs a working group set up to deal with whale and dolphin strandings, said it was not the first time this had happened on the stretch of beach.
"In 1928 the seas were rough and about 103 whales beached on Christmas Eve. It was terrible. They lay there for 10 days crying, their bodies splitting from the heat."
She said there were various explanations for mass strandings and scientists had learnt a lot from strandings on the coasts of New Zealand, Australia and Tasmania. About 80 whales stranded along Hamelin Bay on Western Australia's southern coast in March.
In his book Whales and Dolphins of the Southern African Subregion, expert Peter Best says there are several ingenious hypotheses explaining mass strandings.
One of the newer theories was that a gently shelving sea floor could interfere with echolocation. If cetaceans navigate using the geomagnetic field, then a geomagnetic disturbance could interfere with their navigation and cause them to follow the field inshore.
Alternatively, one or more of the animals in the school may be debilitated through parasitic infestation of the middle ear, for instance, causing them to become disoriented or sick enough to seek out land with others following due to their social bonding.
The phenomenon could be a density-dependent response, in which a population approaching its carrying capacity suffers increased natural mortality.
"It is very likely that no single cause is responsible and elements of some hypotheses may have to act in combination to produce the circumstances for a mass stranding to occur."
Best said in the case of beaked whales it now seemed that human intervention, in the form of mid-range sonar, had been added to the list of probable causes.
Other scientists believe strandings are caused by whales fishing for food too close to the shore or they might have been caught in a rip current, getting their sonar confused.
The stranding could also be due to a navigational error or because an injured or sick animal gives a distress call and the rest of the school comes to it.
Rice, who offers workshops and training on how to deal with mass strandings, said false killer males weigh about 2 200kg and females 1 100kg. She said only trained volunteers should be involved in rescues.
"People only cause the animals further stress. The situation is highly emotional, especially as some of the animals in a bad condition had to be shot."
She said the animals usually beach on their sides and need to be righted.
"It is essential to cool the animal down with water or cover them with seaweed or a wet towel and keep it calm. Stress is the biggest factor and causes them to stop breathing."
She said they should not be returned to the water immediately because they were disorientated and would only beach again. Once they were calmed down, they should be released together.
Some people had suggested that naval exercises in False Bay could have been responsible, but Rice said this was extremely unlikely. There had been no sonar activity close by and this problem was more likely to affect beaked whales.
- This article was originally published on page 4 of The Cape Argus on May 31, 2009
