THE Port River dolphins are jumping for joy – literally.

At least four dolphins have been spotted “tail walking” in the past week.

Tail walking is extremely rare for wild dolphins and had almost completely disappeared from the river after the Port’s most famous tailwalking dolphin, Billie, died in 2009.

Dolphin conservationist Jenni Wyrsta said since last weekend she had seen multiple dolphins walking on their tails, including one called Bianca, who did 33 in a row in sets of two and three.

“I’ve never seen a dolphin do double let alone triple tail walks,” Ms Wyrsta said.

Port River dolphins delight crowds with 'tail walking' Port River dolphins delight crowds with 'tail walking'

“It seems extreme that this has all happened within a week – it’s been years since I’ve seen any tail walking and then this weekend just bang bang.”

Ms Wyrsta said the dolphins had been particularly social lately and had been seen in bigger groups of up to 10 – rather than the usual four or five.

She said a marine biologist had told her that dolphins become more playful when there is an abundance of food. There were a lot of fish in the river at the moment.

media_camera Port River dolphin Bianca showing off a "tail walk" earlier this week. Picture: Jenni Wyrsta

Dr Mike Bossley, who has studied the Port River dolphins for more than 30 years, said he did not know what had caused the outbreak.

Dr Bossley said it was interesting because at least two of the young females who had been spotted performing the trick had mothers who could also do it.

“One of these tail walkers is the young adult female Oriana, and Oriana’s mother is Bianca, who is also a tail walker,” Dr Bossley said.

He said Bianca had almost certainly learned from Billie – the dolphin responsible for Port Adelaide’s wild dolphins learning the skill.

media_camera Port River dolphin Billie performs a tail walking trick in the Port River in 2008.

In the late 1980s, Billie swam out of the Port River and was held at Marineland in Glenelg for a few weeks before being released.

In that time she learnt to copy the captive dolphins who had been taught to walk on their tails. When she returned home, she continued to do it. Before long, several other dolphins were mimicking her.