Children are filming themselves using catapults to kill and torture animals in a UK-wide network on WhatsApp, Sky News can reveal.
Warning: This story contains images and descriptions readers may find distressing
The youngsters - including some of primary school age - have been sharing footage and photos of their kills in groups on the messaging app.
In some videos, injured animals are shown dying slowly after being shot with hand-held catapults.
In others, young people kick and abuse the animals after shooting them - as well as pose holding their dead bodies.
Sky News has discovered nearly 500 members of catapult groups on WhatsApp, in which more than 350 photos and videos have been shared of animals that have been killed or wounded with the weapons.
The RSPCA described the material in the groups as "horrendous" and said it was an "emerging trend".
The "sick" attacks have prompted calls for a change in the law as catapults are not classed as an illegal weapon and can be bought and carried legally.
The animals targeted include pigs, deer, pigeons, foxes, squirrels, pheasants, rabbits, geese and ducks - with one charity saying it had seen an "exponential" rise in birds with catapult injuries.
The Swan Sanctuary, which rescues swans and other waterfowl in Shepperton, has around 20 birds in its care with catapult injuries.
Volunteer Danni Rogers says the "devastating" wounds are mostly to the birds' heads and necks as a result of "pure kill shots".
X-ray images show ball bearings lodged in the birds, as well as shattered bones from the impact of catapult shots.
Describing the "life-changing, death-causing" injuries, Mr Rogers said he had seen "fractures to facial areas, eyes exploding and windpipes bursting".
"I get emotional about seeing animals in distress," he told Sky News.
"(They're) being targeted for no other reason than just pure evil fun."
In one incident, Mr Rogers said he was rescuing a swan with catapult injuries when he was made aware that children with catapults were shooting in the area.
He later discovered a dead pigeon - freshly killed by a catapult - next to his vehicle, which had been left as a "trophy".
Sky News has discovered 489 members - including young children, teenagers and some young adults - across 11 catapult groups on WhatsApp.
In one video shared on a group, a deer lies twitching on the ground, severely injured with a head wound, having just been shot with a catapult by a child.
The young person who attacked the deer then stands over the animal while bringing a hand-held catapult in front of the camera for viewers to see.
Watching it on the floor, the child then kicks the deer, causing it to writhe around in visible distress.
In another video, two teenagers have shot a fox, with one heard saying: "Okay boys... steel shot in the head." The catapult is then held up to the camera, showing the weapon used to kill the animal.
In one video, a teenager holds up a catapult while filming a Canada goose drowning, having shot it from across a pond. While filming the severely injured bird, the attacker is heard celebrating.
"One up for the new catapult, big Canadian goose, dead as a dodo. Get up!" he says.
Separate footage shows a child of primary school age filming themselves picking up a heavily bleeding squirrel while saying: "Look at that boys, it's a ball bearing for ya... have that you prick."
The material in the WhatsApp groups also includes voice notes where children are heard describing their kills.
One boy says in a voice note: "Shot him straight in the head boys, smack bang in the skull, not one bit of kick, nothing, no little flinch before he died."
In another voice note, a boy says: "Goes straight through the rabbit's head."
In a separate voice note, one boy says: "I killed 16 things today lads."
Geoff Edmond, the RSPCA's lead wildlife officer, said the catapult killings were an "emerging trend" and children involved were "deliberately and intentionally targeting" animals "for sport".
"We're seeing more and more injured animals being reported to us that are being hit by catapults," he said.
Police in London and Essex were also aware of increasing numbers of incidents, Mr Edmond added.
While it is not illegal to buy or carry a catapult, when it comes to shooting with one, the law has a number of different pieces of legislation protecting animals.
The first is the Animal Welfare Act 2006, which says that causing an animal unnecessary suffering is an offence.
In the material shared on WhatsApp, a number of the animals are abused while still alive, which again is illegal under the Animal Welfare Act.
Another piece of relevant legislation is the Wildlife and Countryside Act 1981, which protects wild birds and some animals in England and Wales.
This act lists weapons that a person must not use to kill an animal, but catapults are not included in that list.
Henry Smith, the vice chair of the All Party Parliamentary Group for Animal Welfare, says parliament urgently needs to look at changing the legislation.
The MP believes the government should look at ensuring there is a "criminal sanction" for "those who use catapults as a weapon to inflict injury and suffering" and look at restricting sales to under-18s.
Catapults are readily available to buy online, including on websites like eBay and Amazon.
In the catapult groups, young people also trade, sell and even make them by hand, while some people even promote knives.
Mr Smith said: "Until a few people are convicted of using catapults for inflicting great suffering on animals, and they face the consequences of that in law, then there won't be a deterrent to stop other people from engaging in this sick activity."
WhatsApp said the material being shared in the catapult groups was against its terms of use.
A WhatsApp spokesperson told Sky News: "We respond to law enforcement requests based on applicable law and policy."
For more information on how you can help injured or targeted wildlife, visit www.rspca.org.uk.
(c) Sky News 2024: Children using catapults to kill and torture animals before sharing 'sick' images on WhatsApp