Zoo Dolphin Deaths 'Caused By Party Drugs'

Two dolphins that died at a zoo after it hosted a rave were probably killed by a party-goer's heroin substitute, according to a leaked toxicology report.

The dolphins, called Shadow and Chelmers, died at Connyland zoo in Lipperswil, Switzerland last November, just days after the rave.

Thousands of clubbers had attended the weekend rave party after zoo bosses rented out land near the dolphins' training pool.

At first it was thought that the blaring techno music had caused their deaths by damaging the dolphins' sensitive sonar and hearing.

Then prosecutors said that they were considering negligence charges because they believed antibiotics given by zoo vets were to blame for the deaths.

But another toxicology report carried out at the time, leaked to Swiss media, has revealed that the heroin substitute Buprenorphin was found in the animals' urine.

Dutch marine biologist and dolphin expert Cornelis van Elk said: "Opiates are extremely dangerous for underwater mammals and would never be used in any legitimate treatment.

"The reason is that dolphins are conscious breathers which means they actively decide when to come to the surface to breathe, for which they need to be awake.

"Even when sleeping, there is part of the brain that automatically controls the breathing instinct in the same way as it does for people when asleep.

"Drugging them with opiates could well cause this part of the brain to switch off with fatal consequences."

Connyland zookeeper Nadja Gasser said the dolphins, who died within five days of each other, suffered an horrific and slow death.

"He was drifting under the water and was clearly in trouble and so we jumped into the water.

"We tried to hold him. He was shaking all over and was foaming at the mouth," Gasser told local media.

"The death went on for over an hour. It was horrendous. I have not been able to sleep since."

Connyland has consistently denied any wrongdoing.