Here in western WA, it is legal to own a hedgehog. There are breeders here and in Oregon.
Hedgehogs are natural predators of slugs. Folks from naturally-hedgehogged areas encourage them by building habitats near their gardens.
Natural predators of small animals like eagles, hawks, coyotes and cougars may not enjoy eating hedghogs because they are stabby. Even your cats/dogs/roosters etc will probably not enjoy trifling with them.
Hedgehogs can eat cat food which can be treated with black seed oil (per Muhammad, truly "the medicine against all diseases except death") so they don't get ticks.
So why not get one pet hedgehog for each enclosed large garden area? Give them a warm place to hibernate in winter, some food except during hibernation season?
You could wall them off in the garden, turning it into a huge hedgehog coop...no doubt a better idea than trying to naturalize them to the area. I couldn't find evidence of hedgehogs in our Puget Sound ecosystem, and I'm sure that deciding whether they should be introduced is beyond my pay grade. But those are interesting questions!
Thy do eat slugs but its typically a small part of there diet. about 5% is what is typically reported. The problem with them eating slugs is they can get infested with lungworm and if they are severely afflicted it can kill them. So its best to forget about them being a major slug predator.
I used to have a couple pet hedgehogs--they're fun animals. The 2 I had were named Sedge and Holly. The ones we got as pets when I was a kid were the four-toed hedgehog. They're found in the wild in central and eastern Africa and typically live in savannahs. I'm not sure if they would eat slugs or not--they're different than the ones found in Europe which is the type most people talk about online in regards to attracting to their gardens.
A great option here in western Washington is to attract garter snakes. There are a few different species of them in our area but they all eat slugs. And one species feeds mostly on slugs. I've been doing a lot to attract them to my property and the result has been a huge decrease in the number of slugs. Frogs eat slugs too, so do those big black ground beetles--I've seen those beetles working together to eat large slugs. And centipedes eat their eggs.
There are a lot of great slug predators in our area already that you can attract and support.
Henry, thank you for that datum. I would never want to infect them with lungworm, or expect them to eat more slugs than they care to. I come to this forum to disabuse me of crazy ideas!
Daron, I have to admit that I'd like them as pets too. They could have huge runs made of the garden areas and it would be nice to visit with them while working there. If they were great slug killers it would be great news for our local breeders provided we got the hedgehogs nice and humane homes. Maybe they could take Revolution to prevent lungworm, or some other vermicide/preventive like our dogs and cats do. But from the sound of it, they don't eat enough slugs anyway if that is your main aim.
I have tons of garter snakes! Thamnophis elegans, I think they are. Very photogenic as well. Jacqueline Freeman said in the permies PDC that she'd built cairns to house them, and you say the same in your publications...I just need to do more of that. What I have done has definitely increased their population...in my years on land I have perhaps seen twice as many again every year. I have even photographed one eating a slug, just to prove it to the haters, and being snakes they have lots of haters :(
This year I plan to add the pond for frogs -- did you get spawn from somewhere, or attract them?
The big black ground beetles are, now that you mention it, also increasing in number. The slugs love the compost (I think they hatch from the maple leaves I use for carbon), and I wondered recently why so many ground beetles were in the compost...yay!
Somewhere on permies I read of someone using carrion to attract crows, who then picked the land clean of slugs. Maybe I'll try that too. But also a big bucket of Sluggo for last ditch use. I'm not having the losses I've had in previous years. Sure, losses get fewer every year, but my time also gets more precious.