There are fears that a leopard-like cat is on the loose in the fields of Borehamwood after the carcass of a swan was found hanging from a tree.

Six-year-old Carl Parker discovered the swan in fields off Berwick Road during a walk with his mother Sue.

"My son went running towards it, thinking it was a blanket, and when he got closer he screamed," said Mrs Parker, 32, from Rossington Avenue.

About 50 metres from the tree lies the likely killing spot — where hundreds of white feathers lie sprawled across a freshly dug patch of earth.

The swan was killed between Sunday and Tuesday this week, according to Mrs Parker, who regularly walks her dogs in the fields.

Mrs Parker added: "I have found other dead animals with big wounds and a big paw print that was bigger than my dog's."

In January, in the same area, some children came running up to her screaming after finding dead animals including foxes, ducks and chickens and an unidentified in a waterlogged pit.

"I won't take my children up here on my own any more." she said.

Danny Bamping, founder of the British Big Cat Society says it is possible the swan was killed and taken up the tree by a big cat — either a leopard or a puma.

He said: "There's no other animal in the British Isles that could've taken that swan up a tree."

He said that big cats kill their prey in this way so they can continue to eat from the carcass at a later time — but that they would usually leave it higher up so other predators could not get to it.

"It's inconclusive," he said. "It could have been a big cat but I'm not 100 per cent sure."

An RSPCA officer has taken the swan away for a post-mortem to establish how it died.

Animal collection officer, Jill Sanders — former star of the BBC's Animal Hospital — inspected the site and took the carcass away on Wednesday.

She said: "I've never seen anything like this before. It's odd that it's up there in the first place. It could have been foxes if there were four or five of them — especially if a vixen has young.

"The only puzzling point is the tree. I would like to be able to put people's minds at rest and say it was foxes, but how did it get up the tree?"

She also speculated that the swan, which probably came from the lake just north of the site, might have crash-landed in the field, perhaps after hitting nearby power lines.

A spokeswoman for the RSPCA suggested that the swan's body was thrown in the tree by humans.

"When I showed the pictures to our head of wildlife he said there isn't any evidence to show that there's a big cat involved," she said.

"Our main concern is that youths were involved. We've seen them do a lot worse — and it's not just youths. A swan was stoned to death by adults.

"We would urge anyone with information about this incident to get in contact with either the RSPCA or the police."

The fields, which are part of the Green Belt between Borehamwood and Radlett, are privately owned but accessible to the public.

• Police spotted a big cat, thought to be a puma, near Potters Bar in 1998, prompting a helicopter search for the beast.