Hi Don.
No wonder that rat looks anemic. It's lost most of its entrails after being chewed by a cat!
I'll gladly give you the benefit of my extensive pest control experience...
I've tried the most powerful electronic traps and I don't like them because the batteries are too expensive (being six or eight size D with quite limited lifespan). Furthermore, when a rat is zapped they lose their bladder contents and that stuffs pretty stinky and also corrosive to the traps electrical wires. Not only that, they have to be positioned in a sheltered enclosure otherwise the rain destroys them! (although this is not a problem to you using them indoors of course.)
Then I tried CO2-powered units that inflict a blow to the head when the rat knocks a hair-trigger mechanism while going for the bait. They were no good because the bait paste (sold with the trap) wasn't attractive enough to rats, snails and slugs decided
they liked the bait instead, and the mechanism was poorly designed with a slow leak ensuring each Co2 cannister lost pressure well before the bait container ran empty. (And I feared young kids may find the trap, poke their fingers inside, and then further rumours would spread about "the crazy old man in the street"). I tried this type for months and never made a single kill!
So I'm now back to the basics.. That box is there simply to limit the kill to rats and mice only. And since a rat can get through any hole it can fit its head through (and if you don't believe me on this there is a U-tube video that proves it), that entrance can easily be made small enough to stop birds, cats paws, and childrens' fingers etc from getting "whacked".
In my photo the trap is lying on its side and the rats head is caught in a relatively cheap plastic traditional-style rat trap that was placed inside. (At the other end of the box is another mesh screen that sits in slots so it's easily removed for clearing and setting purposes.)
The bait I prefer at the moment is bread smeared in peanut butter and stuffed tightly into the bait-receptacle in the centre of the trigger-pad area.
But I'm always learning... With the larger trap I'm now experimenting with using an whole fresh egg for bait. I know this attracts ferrets and stoats but I'm a little unsure how good it is at attracting rats.. Time will tell. This trap is pushed right under some agapanthus plants to stop birds from going inside (because it has a larger entrance and can kill hedgehogs which are another introduced pest, although many gardeners like them because they eat snails and slugs).
Rats are very timid, cautious and intelligent. But they're also inquisitive and, if a trap is on their normal route and made attractive to them they will eventually summon the courage to explore it. The more they become familiar with its presence, the more they're likely to enter and trip the trigger mechanism.
Hope this helps..