Roland, one of a pair of swans at Markenfield Hall near Ripon, was found dead in the moat on April 14. Staff at the 14th Century manor later managed to capture the suspect otter on film, the BBC reported.
Owner Ian Curteis said the otter was caught on camera after his swan was “completely savaged”.
Roland’s female partner, Sylvia, has been removed for her own safety. Staff said they hoped the otter would move on.
Otters are a protected species in the UK and cannot be killed, captured or sold.
The black swan is native to Australia and was largely brought into the UK for ornamental purposes.
Mr Curteisis a British television dramatist and former television director.
In a career as a television dramatist from the late 1960s onwards, Curteis wrote for many of the series of the day, including The Onedin Line and Crown Court. In 1979, two television plays by Curteis were broadcast: Churchill and the Generals and Suez 1956. The Falklands Play, originally scheduled for production in 1985, was eventually broadcast in 2002.
He is divorced from the popular novelist Joanna Trollope, his second wife. His third wife is Lady Deirdre Hare, daughter of William Hare, 5th Earl of Listowel: together they have restored their home Markenfield Hall.