Surprised how many people are using hazelnuts or peanuts as bait; that's fine if you've just got a few traps in your garden but if you're running big trap lines whole maize is best for several good reasons. Here's two obvious ones; whole maize is about £6-8 for a 20kg bag, and secondly you should be doing bait analysis if you want to trap efficiently. Mice will chew whole maize into chaff, jays/jackdaws etc will remove maize without trace and squirrels will only chew out the kernel, leaving the husks present. While traps baited with whole maize will catch a few reds, greys actually like it, while reds only eat it when they're really hungry so by-catch reduces. Last year when I was trapping greys full-time in Kielder I'd have about 40 traps out, with the doors cable-tied open, this means that I only had to check them once every three/four days and analyse the bait. Only traps where squirrels are present and feeding need to be set live and checked daily. If mice are stripping the bait out so quickly it is reducing the effectiveness of the trap then move it to a different tree and mount the trap on the tree at chest height.