Barbaric cruelty to dolphins Japan tried to hide: Secret film captures use of spikes to stem blood Activist has succeeded in filming barbaric slaughter using "spinal spikes" Fisherman repeatedly stabs a metal rod into the base of a dolphin's head It was shot in a cove during the notorious Taiji "drive-hunts" The footage is now set to ignite international outrage By Nick Constable It is evidence of the horrific deaths dolphins suffer at their hands that Japanese fishermen have tried to keep secret for years. An activist has succeeded in filming the barbaric slaughter using "spinal spikes" - and the footage is now set to ignite international outrage. It was shot in a cove during the notorious Taiji "drive-hunts" and shows a fisherman repeatedly stabbing a metal rod into the base of a dolphin's head behind its blowhole. Another man then rams a wooden plug hard into the wound to prevent the sea turning red with blood, thus alerting marine conservationists. Grim: This picture shows evidence of the horrific deaths dolphins suffer at the hands of Japanese fishermen. This undercover footage shows a fisherman repeatedly ramming a metal rod into the base of the dolphin's head The Japanese Fishing Ministry has maintained for more than a decade that this method is more humane than killing dolphins using traditional spears and clubs. However, the fishermen have been obsessed with ensuring the slaughter takes place out of sight. Before driving the animals into the shallows of a chosen cove, they erect elaborate scaffolding on surrounding cliffs and hang tarpaulins to shield their activities. But one intrepid conservationist managed to find a vantage point to capture the barbaric reality of the slaughter. He hid a remote camera in the cliffs long before the "curtain of horror" was erected and managed to film a killing at close quarters. Upset: Protestor Hannah Fraser, left, and American actress Hayden Panettiere take part in a protest against the slaughter of dolphins by Japanese fishermen The dolphin slaughter at Taiji was first exposed in the Oscar-winning 2009 film The Cove, and it has long been seen by marine conservationists as an exercise in mass cruelty. However, The Cove was unable to gain footage as useful to conservationists as this current video and many of the film's more gruesome scenes were cut out for fear they were too upsetting for audiences. A spokesman for the Whale and Dolphin Conservation Society said the new video provided the first footage of dolphin spike killings at such close proximity. It has enabled a senior British veterinary scientist to write a devastating report on the slaughter in which he says the animals suffer a "profoundly distressing, traumatic and painful" death. Study leader Dr Andrew Butterworth believes the spinal puncture actually prolongs their suffering to an unimaginable four minutes or more. Dr Butterworth, of the University of Bristol Veterinary School, concludes: "This killing method does not conform to the recognised requirement for "immediate insensibility" and would not be tolerated or permitted in any regulated slaughterhouse process in the developed world." A WDC spokesman said of the film: "This is what has allowed a proper scientific assessment. It is the first time this killing method has been independently analysed. It is the scientific analysis of the footage which, the WDC believes, puts mounting pressure on Japan to ban the method. Since uploading the images along with an online petition to its website last week, the WDC has recorded more than 100,000 hits. Among those re-tweeting the link are comedian Stephen Fry, who urges his followers: "Help stop the horror behind the killing of dolphins in Taiji. Check out the shocking footage. Sign the petition. Horrific: Whales are pictured being killed nearby in Taiji , Wakayama Louie Psihoyos, director of The Cove, which won an Oscar for best documentary in 2010, told The Mail on Sunday that he cut out much of his own covert footage of the slaughter. He said: "What we showed in The Cove, no matter how difficult that was for people to watch, was still a Disney version of what actually happens. Having seen first-hand how the Taiji dolphin-hunters treat dolphins while the world is not watching, and having viewed more than 40 hours of covert footage which my team filmed under the secrecy of their tarpaulins, I can safely say that there is nothing remotely humane about the way in which they kill these creatures with their spinal spikes. If we showed the world what actually went on there ... nobody should have to suffer through watching that. These creatures, with bigger brains than us, are sometimes tied up by their tail for hours before they are spiked, geysers of blood spraying with every heartbeat. It sometimes goes on for minutes until they are drained of blood. They thrash and bleed while their mates swim through the blood to try to rescue them. The WDC's campaigns manager Courtney Vail said scientific analysis of the latest footage had "confirmed our worst fears." Awful: This shows a scene from the documentary The Cove (2009) which won an Oscar for best documentary in 2010. It highlighted the slaughter of dolphins She added: "It verifies the unspeakable cruelty taking place behind the tarpaulins." Dr Butterworth said fisherman began using the spinal puncture method 13 years ago after two Japanese scientists claimed it "reduced time to death." However, the covert video, which was neither dubbed nor cut, shows a dolphin still alive four minutes and 14 seconds after the first rod is plunged repeatedly into his back. Animal welfare groups estimate that around 900 dolphins were killed at Taiji during the eight-month season. All will be sold for their meat. Matt Brash, president of the British Veterinary Zoological Society, said at least dolphins were killed comparatively quickly when using traditional hunting practices of clubbing and spearing. "This method supposedly severs the spinal cord - assuming the fisherman manages it," he said. That will stop the dolphins swimming away but then they're just going to bleed to death and drown. I can see there's going to be less blood about because the fishermen are plugging the holes. But that's just a cosmetic way of concealing an atrocious and unacceptable act. Dolphins are beautiful, intelligent and sentient animals and they will know what is happening.