I suspect a dog - especially given that you know them to be around. I second the electric fence if you are free ranging them. Otherwise, you'll want to keep them closed in a secure run. (Even the electric fence does little for hawks and the like. But there are some strategies that can help if you go that route. At least with hawks they usually only take one at a time.)
I have heard that raccoons will get them. If they can fit their hands through the wire of a run they reach and just kill the chicken for the sake of killing them, and also around us I know several who free range theirs only when they are outside with them and they have had hawks try to get them... If you are still free ranging your other chickens you may want to get a trail cam and see if you pick up any animals on there besides the chickens to see what is coming around your property....
In my experience coyote would pick one off each day. I have an automatic door it would wait grab first one at dawn. Raccoon would kill and leave mess. Fox would wipe out flock and steal the bodies one at a time. Weasel would kill for sport get their behind and leave them. Never had a bird predator even though I have them around. Or a dog would kill and maul them up. Good luck finding it. When you do kill it because it knows they are there and will keep returning.
We used 1/2 " hardware cloth to fully close in the run. We have a covered porch/balcony area off of our living room that was was closed in underneath with just lattice (the yard slopes down so the walls under the porch are basement walls) we cut a door size opening in the middle of the front lattice and made a 8x8 run fully covered under a tree that has follage year round, and we covered inside the lattice with the hardware cloth too. we put a door at the other end of the under porch area and that area is covered entirely with the 1/2 in hardware cloth as well. We put the hardware cloth 18" deep into the ground plus put a skirtgoing a foot out also so a predator could would hopefully give up before he got into the enclosure. we put the coop under the porch area and that area is 8' by 20' with probably 12' ceiling to wear the porch flooring is above and that area has about 6 " deep river sand and then in the outside part of run we have dirt and natural mulch with the roosts high enough up so they can run and jump around under it and can use the entire outside run area to play in. When the temps dropped well below freezing we were going to bring them in, but ended up getting an infrared heater (very inexpensive) that we hung about 3-4 feet above the coop just across from it and we keep it on when them temps below freezing. It doesn't warm the room/covered area but they can feel it when they are on top of the coop (which is where they sleep)...its enough to keep them comfortable. We also lined the lattice area that is under porch with thick plastic to help block wind for the sides that there are no walls, and because the sand can get cold, we put large pine shavings on top of the coop against the house in the coop and covered the sand areas with a couple inches of it so they could keep a little warmer when running around during the day. You can see where all they would kick it around and lay and stuff. But anyway, we love the amount of space they have, I am actually trying to talk hubby into making uncovered part of run about 4 feet wider. So far we have had known attempts to try to breach it, except when they first got outside one of our dogs tried to dig but hasn't since. The door entry to the under porch area goes towards our garden so I used cattle grid and green rubber fencing to block that whole area off so I don't have to worry about one of my dogs trying to worm its way into the door if we are in coop area and fail to have door shut all the way.
The kills happened while they were free ranging around dusk, with bodies left behind and intact. Even so I still suspect a raccoon. A trail cam seems like a good investment.
Interesting. My neighbors’ dogs were in their own yard (but barking up a storm) while it happened. We’ve had one get into the yard in the past but it couldn’t get back out, so I don’t know if it could have been them, though.
I’m not sure if killing what killed it is legal where I live - would trapping and relocating work?
An hour before daylight and dark are when most predators attack.
In very many places relocating is illegal. If not, it still makes the predators trap-savvy and pushes a bigger problem then onto somebody else. Plus, it increases chances to spread diseases among wildlife. If you trap, it is best to be ready to dispatch. From a raccoon standpoint, keep in mind they often live in groups, so you may need to trap a lot. And if that works, it buys some time, but eventually more raccoons move back into the area.
