By Paul KirbyBBC News
Agent GreenArthur was the biggest bear in Romania and probably the whole of the European UnionEnvironmental campaigners suspect a Liechtenstein prince shot dead probably the biggest bear alive in the EU on a hunting expedition in Romania in March.
They say Prince Emanuel von und zu Liechtenstein had been granted a permit to shoot a female bear that had caused damage to some farms.
But it was not a female that was shot but Arthur, a 17-year-old brown bear.
The prince who lives in Austria has not yet responded, and the BBC's attempts to reach him have been unsuccessful.
"We don't have a personal problem with the prince," Gabriel Paun of Environmental group Agent Green told the BBC. "We believe the hunting association was meeting his needs."
The office of the Hereditary Prince of Liechtenstein told AFP news agency it did not know the background of this "private and personal matter". But it did stress that nature "has been one of the fundamental concerns of the House and is a central element of the family's commitment to ecological and social sustainability".
Romania's national environmental guard has launched an investigation into the bear's death.
There is no verification that a hunting permit was granted to the prince. However, Agent Green has produced a leaked document that appears to be a permit from authorities to a hunting association in Covasna granting the prince several days in March, and detailing the death of a bear in the village of Ojdula in Transylvania.
Trophy hunting was barred in Romania in 2016 as the brown bear is protected by an EU directive. But hunting is allowed for "problematic" bears that cause damage. Campaigners say a local farmer had complained of an issue with three females and their cubs some time ago, but that the March kill had not solved the issue.
"To get a derogation [permit] you have to prove you've done all diligence. Derogation is the exception and not the rule," said Mr Paun. "Once you extract large bears out of the population you start to destabilise the population so he had a crucial role." Without bears such as Arthur there is a risk of in-breeding, he fears.
Environment Minister Tanczos Barna confirmed that a permit had been issued to get rid of a nuisance bear but did not give details of who received it.
The head of Romania's National Environmental Guard protection agency, Octavian Berceanu, said an inquiry had been opened last week into why a male bear had been shot and that poaching was one of the suspicions of the case.
As females are far smaller than Arthur, activists believe the older alpha male was deliberately targeted for his trophy value of 592.8 points out of a possible maximum 600.
Ann-Kathrin Freude of Austrian environmental group VGT told the BBC that as far as they were aware the shooting of Arthur had produced the highest score ever recorded. "It is a really great trophy to get one of these iconic animals - it's like a good wine."
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