Yesterday a vole came into the lounge and after my wife stopped screaming wondered how you remove such creatures without harming them. Do those high frequency contraptions work and what species do they discourage? We have in the past though of deterring stray cats as well from the garden.
I have 2 such devices in the house and they definitely help. Mine uare plugged into the electric and resonate through the wiring around the house and garage. I do get the odd wee rodent in but usually just after very heavy rain and they don't stay long. As for removing them, there are humae traps which capture the rodents so you can release them outside.
My cats are always bringing in beasties & I just get a jam jar (empty!), scoop them up in it & cover with the lid or a bit of cardboard (they can jump up & bite you) & then let them go outside.