Okay, at my computer!
I'm the proud owner of nine horrible demon cats. We have a love/hate relationship. They're indoor/outdoor, so I've had to deal with the garden issue. (I tried to keep them inside, they kept escaping in magical ways.)
First, what does NOT work.
- Water. I've sprayed my cats with the hose, a super soaker, tossed them in the pool, you name it. Within ten minutes they will be back. It's domesticated cats that dislike water, mostly because they aren't raised around it. It's not that they're 'afraid' of it, they just don't 'get' it. Soon enough it will become more annoying than anything and they will ignore it.
- Those cat repellent sprays/pallets they sell in the stores. They work when FRESH. Once the smell has settled - ESPECIALLY if it's outside - they'll go right back to where they were. Don't bother, they're a waste of time.
- Pepper. Some cats dislike it, mine don't care. If they're desperate enough for something it won't keep them away. Smells as a rule work only when fresh. After it's settled the scent isn't strong enough to keep them away.
-Yelling. The cat will just figure out how long they have until they need to be gone. They will time it to a second if you let them.
So what DOES work?
- Fresh orange peels, orange sprays, etc. But ONLY if fresh! Some peppers, again if fresh.
- Loud noises. Sudden things happening. Anything that startles them. I personally used motion activated cat sprays. They're a mix of pheromones that scare the cat, as well as a loud "Ssssst" noise. Much like these off Amazon. You want ones that are LOUD, sudden, and not easily seen.
- Other people have had a lot of success with motion activated sprinklers, like these. I've never personally used them, but they're worth a try.
To cat proof your coop, just repair any holes you find. Seriously, it's just 'wait until kitty escapes through, repair it'. Sooner or later they WILL run out of holes to go through. When my cats became indoor cats I'd still find them outside all the time. They'd sneak out through a tiny hole in my garage door, sneak out from the TOP of my garage door, pull the screen out of the window. You really have to catch the cat in the act and repair it. And repair it WELL. You want something the cats can't break. NO twine, rope, etc. You want wire. A cat WILL chew through the rope in time. You need something they can't tug at.
If kitty is pulling the fence up, repair it with stakes in the ground, and make sure it won't budge. If kitty is climbing through the roof, put some mesh screen over it and nail it in. If the cat comes in through the ground (Digging a hole) you put bricks down.
Yes, it's HORRIBLE, and it's more work than whacking the cat with a shovel. But I promise the cat WILL get bored eventually. He may sit outside the pen and watch, but after a while he won't try to get in. It's an uphill battle, but it CAN be won.
As for the cat not being in their yard, I get it, I really do. But cats are meant to be outdoor creatures - humans were the ones who put them in houses. It's their nature. Imagine it this way, if you were raised in a basement and never saw the outdoors, you would be fine. The outdoors is neat, but it's not something you think about. But if you were raised indoor/outdoor - like most humans - then suddenly not being able to leave your house ever can be *very* hard. You can adapt, but it's hard. Yes, a cat WILL adjust, and will be fine, but it's the humans you have to worry about. The humans can't be that 'mean' to their 'baby'.
As for killing the cat, DO NOT DO THIS PLEASE FOR THE LOVE OF ALL THAT IS HOLY. That cat may be a horrible pain to you, but it may mean the world to the girlfriend. When my cat vanished I didn't get over it for YEARS. Please, whatever you do, don't do that. It's cruel to the cat. He doesn't know better. Talk to the ones who SHOULD know better, his human.
As for the human issue, try to be polite when you talk to him. Don't be emotional. Don't say "That was my favorite therapy duck!!" leave that out, as much as you'd like to yell. Don't be angry, don't be sad. It triggers the defense emotion in people and makes them less likely to help. Let them know that their cat ruined your property - Property, NOT your pet. Animals are considered property in most places - and you'd like to figure out how to prevent this from happening again. Don't go straight into "Pay for this" as it triggers defense again. tell them what you're doing to prevent it on your end, so they feel like it's a give and take situation. They'll be more likely to help that way. (It sucks, but trust me, it will keep the relationship happier in the long run.)
In the even he goes straight into "That's not my cat, you're an idiot, I'm not doing anything because he's behaving like a cat" tell him your husband wants to murder it. Maybe tell the girlfriend. If you can talk to them together, that's perfect. Then it's not your word vs his. If you have animal laws, or property laws, see if they cover that. They *should*. It would fall under property damage. If your laws are similar to the US, then legally his property destroyed yours. Much like his car hitting yours. He would legally be required to pay for your chickens, ducks, and damage to your coop. If you have laws like that, and push comes to shove, it may be wise to bring a copy with you. He could also be on the hook for any vet bills you get.
Other things you can do is take kitty to the shelter. Often once is enough to keep the humans from letting them out again. If your laws allow it, call the police to report it. Has the cat been fixed? Often times not being fixed makes them wild. You could in theory get into trouble for it, but you could take the cat to be neutered. He would settle down then, and be at less of a risk for sicknesses.
In the end, when it comes to cats being a pain, it takes both the owner AND the human being attacked working together to fix the issue. It won't happen overnight, either. My cat took months to convince to leave my finches alone (She's an extreme case, though). But it CAN be done, don't give up. Don't let the cat ruin your day, and keep on enjoying what you want to do.
And please, don't blame kitty too much. It's not his fault his human is an idiot and doesn't restrain him. He's just doing what cats do - hunting.
(NOT saying cats are more important than chickens!!!! Just saying training them is harder than chickens due to how stubborn they can be. Also NOT saying it's 100 percent not the cat's fault. It is. But it's more the human's fault for not keeping him in check. Often the humans don't even know what kitty is doing.)
I'm the proud owner of nine horrible demon cats. We have a love/hate relationship. They're indoor/outdoor, so I've had to deal with the garden issue. (I tried to keep them inside, they kept escaping in magical ways.)
First, what does NOT work.
- Water. I've sprayed my cats with the hose, a super soaker, tossed them in the pool, you name it. Within ten minutes they will be back. It's domesticated cats that dislike water, mostly because they aren't raised around it. It's not that they're 'afraid' of it, they just don't 'get' it. Soon enough it will become more annoying than anything and they will ignore it.
- Those cat repellent sprays/pallets they sell in the stores. They work when FRESH. Once the smell has settled - ESPECIALLY if it's outside - they'll go right back to where they were. Don't bother, they're a waste of time.
- Pepper. Some cats dislike it, mine don't care. If they're desperate enough for something it won't keep them away. Smells as a rule work only when fresh. After it's settled the scent isn't strong enough to keep them away.
-Yelling. The cat will just figure out how long they have until they need to be gone. They will time it to a second if you let them.
So what DOES work?
- Fresh orange peels, orange sprays, etc. But ONLY if fresh! Some peppers, again if fresh.
- Loud noises. Sudden things happening. Anything that startles them. I personally used motion activated cat sprays. They're a mix of pheromones that scare the cat, as well as a loud "Ssssst" noise. Much like these off Amazon. You want ones that are LOUD, sudden, and not easily seen.
- Other people have had a lot of success with motion activated sprinklers, like these. I've never personally used them, but they're worth a try.
To cat proof your coop, just repair any holes you find. Seriously, it's just 'wait until kitty escapes through, repair it'. Sooner or later they WILL run out of holes to go through. When my cats became indoor cats I'd still find them outside all the time. They'd sneak out through a tiny hole in my garage door, sneak out from the TOP of my garage door, pull the screen out of the window. You really have to catch the cat in the act and repair it. And repair it WELL. You want something the cats can't break. NO twine, rope, etc. You want wire. A cat WILL chew through the rope in time. You need something they can't tug at.
If kitty is pulling the fence up, repair it with stakes in the ground, and make sure it won't budge. If kitty is climbing through the roof, put some mesh screen over it and nail it in. If the cat comes in through the ground (Digging a hole) you put bricks down.
Yes, it's HORRIBLE, and it's more work than whacking the cat with a shovel. But I promise the cat WILL get bored eventually. He may sit outside the pen and watch, but after a while he won't try to get in. It's an uphill battle, but it CAN be won.
As for the cat not being in their yard, I get it, I really do. But cats are meant to be outdoor creatures - humans were the ones who put them in houses. It's their nature. Imagine it this way, if you were raised in a basement and never saw the outdoors, you would be fine. The outdoors is neat, but it's not something you think about. But if you were raised indoor/outdoor - like most humans - then suddenly not being able to leave your house ever can be *very* hard. You can adapt, but it's hard. Yes, a cat WILL adjust, and will be fine, but it's the humans you have to worry about. The humans can't be that 'mean' to their 'baby'.
As for killing the cat, DO NOT DO THIS PLEASE FOR THE LOVE OF ALL THAT IS HOLY. That cat may be a horrible pain to you, but it may mean the world to the girlfriend. When my cat vanished I didn't get over it for YEARS. Please, whatever you do, don't do that. It's cruel to the cat. He doesn't know better. Talk to the ones who SHOULD know better, his human.
As for the human issue, try to be polite when you talk to him. Don't be emotional. Don't say "That was my favorite therapy duck!!" leave that out, as much as you'd like to yell. Don't be angry, don't be sad. It triggers the defense emotion in people and makes them less likely to help. Let them know that their cat ruined your property - Property, NOT your pet. Animals are considered property in most places - and you'd like to figure out how to prevent this from happening again. Don't go straight into "Pay for this" as it triggers defense again. tell them what you're doing to prevent it on your end, so they feel like it's a give and take situation. They'll be more likely to help that way. (It sucks, but trust me, it will keep the relationship happier in the long run.)
In the even he goes straight into "That's not my cat, you're an idiot, I'm not doing anything because he's behaving like a cat" tell him your husband wants to murder it. Maybe tell the girlfriend. If you can talk to them together, that's perfect. Then it's not your word vs his. If you have animal laws, or property laws, see if they cover that. They *should*. It would fall under property damage. If your laws are similar to the US, then legally his property destroyed yours. Much like his car hitting yours. He would legally be required to pay for your chickens, ducks, and damage to your coop. If you have laws like that, and push comes to shove, it may be wise to bring a copy with you. He could also be on the hook for any vet bills you get.
Other things you can do is take kitty to the shelter. Often once is enough to keep the humans from letting them out again. If your laws allow it, call the police to report it. Has the cat been fixed? Often times not being fixed makes them wild. You could in theory get into trouble for it, but you could take the cat to be neutered. He would settle down then, and be at less of a risk for sicknesses.
In the end, when it comes to cats being a pain, it takes both the owner AND the human being attacked working together to fix the issue. It won't happen overnight, either. My cat took months to convince to leave my finches alone (She's an extreme case, though). But it CAN be done, don't give up. Don't let the cat ruin your day, and keep on enjoying what you want to do.

And please, don't blame kitty too much. It's not his fault his human is an idiot and doesn't restrain him. He's just doing what cats do - hunting.
(NOT saying cats are more important than chickens!!!! Just saying training them is harder than chickens due to how stubborn they can be. Also NOT saying it's 100 percent not the cat's fault. It is. But it's more the human's fault for not keeping him in check. Often the humans don't even know what kitty is doing.)