There are calls for a captive SeaWorld killer whale to be freed into the wild after activists filmed her beaching herself on a concrete slab at the side of a pool at a Tenerife tourist park.

It shows the orca called Morgan fully out of the water at Loro Parque, almost motionless, at the end of a show.

A clip, filmed anonymously by 'Morgan Monitors' and posted onto the website of the Dolphin Project which campaigns against the captivity of dolphins, shows spectators walking by oblivious.

She was said to have remained there for around 10 minutes, moving occasionally, as some tourists reportedly stopped to take selfies with her.

In April, reportedly, Morgan was recorded repeatedly banging her head into a metal grate.

The Dolphin Project said while it could not explain the reason for her behaviour, "the juxtaposition of a previously-wild orca against the stark backdrop of the park's performance area is unsettling".

But Loro Parque said it was "absurd" to draw conclusions from a few minutes of footage of Morgan and said activists were interpreting the images "simply with an anti-zoo objective".

It said in a statement: "Voluntary stranding is a natural behavior in wild orcas.

"The orcas at Loro Parque are trained to leave the water on their own accord. This behavior is used for manifold purposes, for example, for presenting the animals to the public, for conducting corporal check-ups, for inspecting their blowholes, as well as for testing hearing abilities of the orcas.

"During their free time, sometimes animals get on stage, even go sliding from side to side. This is done quite naturally, often associated with game dynamics.

"Pretending that's a stress test shows an enormous ignorance about the behavior of these animals."

Lincoln O'Barry, of the Dolphin Project, told Sky News: "When you put a sonic creature in a concrete box they stop using their primary sense which is their sonar, they are just basically bored.

"When you put them in an unnatural environment they are going to behave unnaturally."

Since the emergence of the footage, a #FreeMorgan campaign on Twitter has attracted fresh support.

One Twitter user wrote: "#FREEMORGAN #Tenerife @SeaWorld These beautiful animals do not belong in captivity. Visitors to Tenerife please don't go to @LoroParque."

Another tweeted: "Killer whales don't deserve to be in humans' tanks. They deserve to live in the ocean fgs. #FreeMorgan."

According to the Free Morgan Foundation , a charity dedicated to her release, Morgan was captured by Dolfinarium . a marine mammal park in Harderwijk, the Netherlands, in 2010, under a 'rescue, rehabilitation and release' permit.

However, following an assessment by an independent team of experts, the Dutch theme park concluded she was not suitable to be released into the wild. She has been at Loro Parque since November 2011.

Kenneth Balcomb, executive director of the Washington-based Center for Whale Research, told Sky News: "The Loro Parque statement is simply spin-doctoring in service of the usual fantasy that it is 'normal' for such amazing animals to be used for financial gain in captive entertainment.

"That is an astonishing demonstration of behavior! While these whales are trained to slide out for some veterinary inspections and procedures, this apparently voluntary slide out appears to be more of a demonstration of messaging ... who really knows what is going on inside of that whale's amazing brain?

"The most striking features of the video for me were the extreme fatness of the body, and the slow motion head and tail lifts as if posing. I would not consider either of these features normal for free ranging killer whales in the Pacific Northwest."

Orcas are the largest member of the dolphin family and can swim up to 100 miles a day.