Victoria Gill is a science correspondent for the British Broadcasting Corporation.
eBay banned the sale of elephant ivory, but sellers are listing it under different names.
The ivory objects were often listed as bovine bone.
The items were tested in an independent lab after we purchased them on eBay. There were two that were made of ivory.
Thousands of ivory objects have been sold on the site since the company banned its sale.
The investigation was begun by Dr. Cox. She and other ivory trade experts are worried that online trade could undermine the ban on the sale of ivory in the UK.
More than a decade ago, BeBay announced a complete, worldwide ban on ivory sales. An online post stated that the global ban would protect buyers and sellers.
Dr Cox and her team tracked bovine bone on eBay's UK site over the course of three months. More than 500 pieces of bovine bone were determined to be ivory by the team.
Dr Cox was able to use pictures and information in listings that provided buyers and investigators with clear evidence of what the objects are actually made of for this online forensic study.
She said that the colour of ivory has a creamy hue. The weight of the item being sold will often be mentioned in a listing.
An object's image is the key piece of evidence. You can think of carved ivory as a tree ring but for teeth and tusks. According to Dr Cox, these are unique to ivory.
Law enforcement officers and investigators have used these techniques to identify illegal ivory in the past.
Three objects listed on eBay as bovine bone were bought by the news organization.
Scientists at the Oxford University School of Archaeology confirmed that two of the items we bought were replicas of elephant tusk.
eBay said that it had been working to tackle the illegal trade in elephant ivory for over a decade.
In the past two years, we blocked or removed over 265,000 listings that were not in line with our animal products policy, according to a spokesman.
"Our proactive approach means that ivory sellers are forced to use obscure code words for items which are rarely sold because buyers cannot find them."
500 eBay sales of ivory were tracked by the ivory trade experts over the course of three months. The same code words were used many times.
There are differing laws on the ivory trade in different countries. The UK brought in a ban on the sale of ivory on Monday. It is illegal to trade in elephant teeth and tusks in the UK from June 6th.
Wildlife traders exploit other online platforms like eBay. In our investigation of the pet trade in apes, we found that animals were being advertised on the social media platform.
In April of this year, researchers from a campaign group published a report saying that there were129 pieces of potentially harmful wildlife trafficking content on Facebook.
Facebook's parent company Meta said that they don't allow the trading of wildlife or their parts. Meta is a member of the coalition.
John Scanlon is the CEO of the Elephant Protection Initiative Foundation.
He said that they are an efficient vehicle for criminals to sell illegal goods in any country. It's troubling when an online platform makes big commitments but fails to deliver.
The new UK legislation is the latest example of the international community closing down legal ivory markets. This progress is at risk of being undermined by online leaks.
The threat to Africa's elephants are changing.
"Poachers still target ivory in central Africa, but it has been reduced in parts of eastern and southern Africa." As the impact of climate change is beginning to be felt, we believe that the biggest emerging threat is the increasing competition between humans and elephants for land and resources.
Wildlife trade experts are concerned that if platforms are not policed, more ivory could move online, especially if national legislation is tightened.
Dr Cox said that sites like eBay allow millions of sellers to advertise across international borders.
She said that the company's failure to enforce its ban on the trade in ivory gave a safe space for a trade that threatened wildlife.
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