Well the defence mechanism is a stupid theory..... you aren't supposed to end up worse off when deploying a defence mechanism!

It could be that they're out at night eating slugs that like the dark and damp. If the slugs have been treated with a slug repellant, they may be causing a buildup of gas internally. Can toads fart?

I had a cat that liked eating slugs. She also liked eating slug pellets. The pellets were OK for pets if eaten but not recommended. Cat ate slugs, cat OK. Cat ate slug pellets, cat OK. Cat eats slugs that have eaten slug pellets ~ bright blue cat puke all over the house.

LTS