First the context, to hopefully avoid unhelpful anti-cat remarks: I am a cat lover and I live in a rural area. This is farming country, not bush land, and it is already overrun with feral cats. It is not an area that harbours endangered species. The wildlife my cats bring home consists of mice, rats and the odd sparrow. 

My cats are pets but they are also farm cats. They wander freely and do an excellent job of keeping the rodent population in check. They have access to the house and I want to keep it that way because they like to sleep with me at night and I enjoy their company. 

The problem is that they have started stashing carcasses of their victims under my bed. Sometimes I discover them in time. Otherwise the smell alerts me. It is really disgusting, especially if I only become aware of it after I have already gone to bed. 

My question is if there is any tactic, product, idea or item that can prevent this behaviour. I know the cats regard my bed as their den. I raised them from tiny kittens and they have always slept with me. They never deposit anything horrible on the bed, but they seem to think the space underneath is okay. Can anything be done to stop this? 

I don’t want to get a dog instead, or lock the cats outside, or squirt them with ammonia, or anything like that so let’s please skip over those kinds of suggestions, but if anyone knows an effective way of teaching cats that a particular place is off-limits for depositing prey, I would really appreciate hearing about it.