The two young women who arrived at Heathrow in February 2014 en route to Düsseldorf were carrying nondescript luggage. Customs officers were suspicious nevertheless and looked inside – to find 13 iguanas stuffed into socks inside the cases. Astonishingly, 12 of the highly endangered San Salvador rock iguanas had survived their transatlantic journey.

“There only about 600 of these animals left in the wild, in the Bahamas, and these animals were being taken to a private collector somewhere in Germany. Incredibly, we were able to return 12 of them, alive, to their homeland – on San Salvador island,” said Grant Miller, who was then working for the Border Force’s endangered species team.

The incident remains one of the strangest attempts at wildlife trafficking in recent years and reveals the extent to which individuals will try to break the law to obtain endangered animals for their collections, or to buy body parts to consume for their alleged medical properties, or as exotic food. Illegal wildlife trade is now the fourth most profitable form of trafficking in the world, after drugs, guns and humans.

And it is a trade that is increasing dramatically, ranging from the smuggling of the occasional, individual rare creature – like the endangered Chinese giant salamander that was recently found inside a cereal box brought into the UK – to the trafficking, for their meat and scales, of more than half a million pangolins from Africa to Asia over the past three years. In this latter case, two of the world’s eight species of pangolin are now rated as being critically endangered and there are serious concerns about numbers of the others.

In addition to pangolins, other endangered trafficked animals include elephants, rhinos, European eels and seahorses. Finding ways to halt the widespread loss of these creatures is now becoming a desperate problem, say conservationists, and will be the focus of a meeting, “Can surveillance technology and social science address rule-breaking and wildlife crime?”, to be held this week at the Zoological Society of London.

The conference organiser, Tom Letessier, said one of the most worrying forms of illegal wildlife trade was the killing, on a vast scale, of sharks – in particular grey reef sharks and thresher sharks in the Indian Ocean. “Their fins are cut off and the sharks are dumped back into the sea to drown. Their fins then end up as food for banquets for the rich in south-east Asia,” he added.

Chinese giant salamander. One was recently found in a cereal box brought into the UK. Photograph: Nature Picture Library/Alamy

As a result, thresher sharks are now considered to be vulnerable to extinction, while grey reef sharks are rated as being “near threatened”. But what can be done?

One idea is to use technological fixes – such as drones which could be flown over ships to film crewmen in the act of dismembering sharks, said Letessier. “The development of increasingly accurate devices, such as synthetic aperture radar for satellites, would also allow authorities to monitor illegal fishing from space in real time,” he added.

“However, it is equally clear that we have to consider social factors when working out why people turn to illegal wildlife trade. Stocks of fish on which local villages depend could become depleted and fishermen have to turn to something else. Sometimes the only thing on offer is a creature that is legally protected.”

This point was backed by Fran Cabada, a marine biologist at ZSL. “Fisherfolk across the world have a very close relationship with the sea,” she said. “If you try to find them a different job, say in a factory, they will not want to take it. They prefer jobs that allow them to be at sea, even if the work there is illegal. So again, we have to include social and economic factors when understanding and tackling illegal wildlife trade, both at sea and on land.”

In addition, the illegal wildlife trade is often linked with organised crime so it may simply be that local people feel compelled to join in, added Cabada.

Miller, who now works for ZSL, agreed. “The organised criminal is always looking for the next opportunity to hammer a particular species. We will see that in the next few months in the UK with the beginning of the fishing season for the European eel. Organised criminals will try to source elvers and ship them out of Europe to markets where they can be made into finished products and then sold round the world – not as endangered European eels but as Japanese eel or American eel. However, gene-testing techniques have recently been developed that allow us to tell very quickly if eel is arriving in a port but is not what it is claimed to be. It is all part of an ongoing battle.”