Police officers seized a baby monkey at a motorway service station after its owner had advertised it for sale for £4,000, a Swansea court has heard.
Jason Allen denies causing unnecessary suffering to the animal
Jason Allen, 33, from West Cross in the city drove to the rendezvous in June 2005 believing he was meeting a buyer for the black capped capuchin.
Instead, it was seized following the undercover RSPCA operation.
He denies causing unnecessary suffering to the baby monkey by forcing its separation from its mother.
A judge sitting at Swansea magistrates court heard that the RSPCA spotted an advert for the baby monkey in a publication called Cage and Aviary Birds Weekly in April last year.
Andrew Shipp, of the RSPCA prosecution unit, said the animal was also advertised on the internet.
He posed as a buyer called Terry, from Staines in Middlesex, and telephoned Mr Allen to find out more.
In a recorded conversation, the court heard Allen claimed that the baby was nine-to-10 weeks old.
The black capped capuchin is native to south America
Mr Shipp: "Is it right to come away from its mother like this?"
Allen: "I have taken them at two to three weeks old. It's not a very nice thing to do. The mother obviously does not like it, and the baby was upset for about a day."
He told Mr Allen that his wife already owned two adult capuchins and that he wanted to buy the baby from him.
Mr Shipp was told that a buyer in Manchester had been willing to pay £2,850 and he agreed to pay £3,200.
A meeting was set up at the Leigh Delamere service station on the M4 in Wiltshire on 3 June 2005.
But when he got there he was met by two police officers, three RSPCA inspectors and experts who seized the baby and took it to Monkey World in Dorset, where it was later reunited with its parents.
The court heard Mr Allen, who had a dangerous wild animals licence, had owned the parents for about 18 months and kept them in his back garden.
In police interview, he said the baby was born on 27 January 2005 and claimed he was selling it because it was being rejected by its parents.
Expert advice to the RSPCA suggested that the separation of the mother and baby would cause both stress and trauma.
A weaning period for a baby capuchin can be up to two years.
The case is listed for four days.