The thieves are expected to try to sell the horns in Asia. Europol claimed in 2011 that most of Europe's illegal rhino trade was committed by a single 'ethnically-Irish organized criminal group.'
The heads were taken late Wednesday by three masked men from the premises in the National Museum Archives in the town of Swords in County Dublin, ten miles north of the capital city.
Three masked men entered the building, tying up a security guard on duty at around 10:40 p.m. Wednesday night. Around an hour later the thieves absconded in a large white van. Shortly after midnight the guard managed to free himself and called the police.
A statement from the National Museum of Ireland said the likely destination for the head was Asia. "The stolen rhinoceros heads have a total of eight horns that have probably been taken to supply the illegal trade in powdered horn that is used in traditional medicines in the Far East," it said.
The black market value of heads is estimated to be in the region of €500,000 ($652,200). A single horn can fetch as much as $260,000.
"Because of the nature of the trade being illegal we can't guarantee where they're going, but the demand is coming from Asia. In Vietnam in particular, there has been exponential growth in demand, not only as an anti-fever remedy, but also as a totally unproven cure for cancer and even a trendy substance people take to cure hangovers," she says.
WWF figures indicate the demand is not only an issue for museum collections, but also wild animals. In South Africa alone, over 200 rhinos have been illegally killed in 2013 alone. In 2012, 668 were killed, whereas in 2007, only 13 rhinos were killed.
"In terms of the impact on wild populations, these horns are coming from animals that have been dead for a long time in most cases, but it does have an impact on wild populations and other species by encouraging poaching. You have to look at the illegal trade from source to end-user," says Ms. Sohl.
A paper published in the journal Science this month saw four leading conservationists called for the creation of a legal trade in rhino horn, but Sohl says the WWF does not support this idea.
Ironically, fear of theft may have itself played a role in the robbery. The National Museum of Ireland, like many other collections, took the decision to remove all rhinoceros horn from display due to increasing thefts of rhino taxidermy. The stolen specimens were placed in storage over a year ago.
In 2011, the European Union's policing coordination body, Europol, issued a report stating that Europe's illegal trade in rhino horn was predominately the result of a single "Irish and ethnically-Irish organized criminal group," known to use intimidation and violence to achieve its ends. It has been implied the group are from the Irish Traveller community, or Pavee, a nomadic group on the margins of Irish society.
Martin Collins from the Traveller lobby group Pavee Point says people should not jump to conclusions. "I would suggest here that it's downright irresponsible for Europol or anyone else to make these kinds of statement, unless they can be substantiated."
"They also need to be careful they don't incite hatred toward the Traveller community, tarnishing a very particular and identifiable ethnic minority."
Mr. Collins questions the validity of indicating Traveller identity, as some reports in recent months have done. "It may be the case that there are a number of individuals who happen to be Travellers involved, I don't know, [but] we don't ethnically identify those responsible for reckless lending that plunged us into the worst recession in decades," he says.
In March 2013, a Limerick man, Michael Kealy, was extradited to Britain to face charges of stealing a rhino horn from an antiques dealer. While in custody on an international arrest warrant, Mr. Kealy told Irish police: "I just witnessed the crime."