Decomposed in 2 weeks? Aye, right. Way more than 2 weeks, especially at this time of year with cooler temps in attic.
We live in an old cottage out in countryside next to fields. Every year in the weeks after harvest the mice having been evicted from their cosy nests, decide it's time to come inside in the warm.
Tried baited traps but somehow mice mostly avoided getting croked till I got several traps that mice just need to run over to get caught.
Mice prefer running along edges like skirting boards so replicated similar in attic as I knew the rough point where they got in. Made a 3 sided skirting board height box, open topped. in the closed end added another wee board just wider than a trap length away from end board to create a narrow space.
This board was shorter by the width of a mouse at both ends so they had access to the narrow space. In the middle put a small saucer with poisoned blue coloured grain. The mice had been eating this previously, they loved it, then wandering off to snuff it in places in walls and attic inaccessible to us, that's how we know 2 weeks ain't near long enough.
With 8 traps, eight, I put 2 on each of the sides with the trigger plate next to "skirting boards" so mice would walk over trap. The narrow space had another 4 with them either side of bait/poison saucer. The first night this was in operation caught 7 mice. Four in about an hour or so which were removed as we could hear traps getting triggered, the other 3 after we went to bed. After that maybe 1 a night for a week or so.
I adapted some of the traps that required to be baited, with a 30mm square of thin aluminium pop riveted to the bit the bait went on. Worked perfectly like the other pressure trigger traps. As for humane traps, the wee bastards will just come back.
On that note, a mate and I were staying in an old cottage restored by his climbing club near Achnasheen. Middle of summer there was a wee moose running about round edges of floor, wasn't scared of us. We caught it, took it outside and let it go. It was back inside as quick as we were. We caught it again, took it a lot further away, once again it came back, took longer though. When we managed to catch it again, it took wee bit longer,
this time it was released much, much further away but crucially at the other side of a burn running past cottage. Never saw or heard it again.