"Two dead dolphins 'forgot to breathe after taking heroin substitute following zoo's weekend-long rave' "
http://www.dailymail.co.uk/news/article-2140362/Connyland-zoo-Two-dead-dolphins-killed-heroin-substitute.html
I'm not sure if it was an accident, or if they did it on porpoise
Two dolphins who died a slow, agonising death 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 within five days of each other at a zoo in Switzerland last November.