I doubt gumballs will deter any form of wildlife. Cactus are far more pokey and snakes love to hang out around them.

I have better luck with tiny bowls of beer to control slugs. The copper tape stuff works but slugs will eventually find a route up and over.

Regrettably, your response just makes too much sense, John.
Since I asked, I googled and it seems that many people use the gumballs as mulch in their planters on top of the soil and find it helpful so I'm going to try loading up these
nooks with gumballs anyway. Couldn't hurt to try.

The folks from the Pacific northwest recommend the copper
tape/wire treatment as well as the slug geta bait and those folks have continuous problems with slugs so I figure they're the experts.
I've used the beer in low bowls but it's a nuisance to have to empty and fill them daily. I read that flat beer with alcohol evaporated out doesn't work so it's a continuous chore of dumping and refilling.

I have read that gumballs work to deter slugs for hostas. However, I never tried it. My hostas are bait for the deer, to entice them so that they don't work on my trilliums. Still have a few hostas, but after years of being munched, they are small. (Have to say hostas are beautiful plants for a city garden that doesn't have to fend off critters.)