As many as 100,000 of the highly intelligent and sociable animals were in the rarely-seen 'super-mega-pod' off the coast of California.

London - It could have been a feeding frenzy. It could simply have been an exuberant get-together.

But something made tens of thousands of dolphins gather in a single patch of the Pacific Ocean and deliver a vast and thrilling spectacle of boisterous acrobatics.

About 35 square miles of water were churned into a blue-grey mass of leaping dolphins and sea spray.

As many as 100,000 of the highly intelligent and sociable animals were in the rarely-seen ‘super-mega-pod’ off the coast of California.

“They were coming from all directions, you could see them from as far as the eye can see,” Joe Dutra who witnessed the incredible sight just north of San Diego.

Mr Dutra, who captains Hornblower Cruises, was out on his daily tour with a boat full of whale watchers when the pod was spotted.

“I’ve seen a lot of stuff out here but this is the biggest I’ve ever seen. When you see something like that it is honestly truly beyond belief. You had to be there to experience it. It was truly spectacular.”

Mr Dutra estimated there were about 100,000 adult and juvenile short-beaked common dolphins swimming in the area. Others say the true figure is likely to have been considerably lower, and closer to 10,000.

However, even this is still vastly greater than the usual pod size of 15 to 50 commonly seen in coastal waters, including those around Britain.

The species is the most common in the world. They typically live for up to 35 years, grow to about 7ft in length and weigh around 500lbs. They are widely found in the Pacific and Atlantic oceans and are regularly seen in British waters.

Whale and dolphin watching tours off California have done particularly well this year, with dozens of animal sightings reported up and down the coast.

But experts were uncertain why so many were travelling together on this particular afternoon last week.

US marine expert Sarah Wilkin said that several pods may have come together to feed on the plentiful supply of sardines, herring and squid in that part of the coast.

“They’re attracted to kind of the same thing, they might wind up in the same place,” she said.

The charity Whale and Dolphin Conservation, agreed that the animals may have been drawn in from miles around by food. They may also have just been having a party.

Nicola Hodgins, a marine biologist with the charity, said: “These are incredibly energetic, sociable, boisterous and acrobatic animals.

“They could just be enjoying themselves. It could just be a social gathering. The likely answer is that they were following food. But I think they were also probably having a great time.”

Dolphin expert Peter Wallerstein, who runs California-based Marine Animal Rescue, said: “In my experience it’s all about the food.

“There is so much squid in the water at the moment and that is what the dolphins are chasing. The big pods are usually a little bit further offshore but they are following the food source.

“They have very close-knit social structures. They have extended families and pods stay together for generation after generation. There’s a hierarchy and the families that are related to one another will help mothers raise their calves.

“But they are not the cuddly creatures some people imagine. They have their battles and can be very aggressive with one another, but they are very intelligent.”

British experts said that ‘super-mega-pods’ of around 10,000 do occur occasionally but often go unseen because they have formed far out to sea.

There are some three-million short-beaked common dolphins worldwide. - Daily Mail