http://www.homedepot.com/p/JT-Eaton...pvNiUwmoAXB8CjgnwmFI_5HWoQ4zH9Hn_4aAiX88P8HAQ
The above link is for a rat bait box. I just found one quick but a better search will provide a larger hole than that triangle. I use them, and they not only keep the rat population down but squirrels will feed from them. Chickens, children and anything larger than a red squirrel are safe. The chunx bait poison isn't scattered around for other animals to pick up like with pellets. A good safe pest management system. But yeah, search around and find one with slightly bigger hole. Take food in at night and leave bait box in pen, even taking food in for period of day so squirrels would use the boxes would be ideal. Rats are everywhere and if you don't start with a management for them before you know it there will be 3, 4, 6 holes with estimates of a dozen rats per hole around your pen.
The above link is for a rat bait box. I just found one quick but a better search will provide a larger hole than that triangle. I use them, and they not only keep the rat population down but squirrels will feed from them. Chickens, children and anything larger than a red squirrel are safe. The chunx bait poison isn't scattered around for other animals to pick up like with pellets. A good safe pest management system. But yeah, search around and find one with slightly bigger hole. Take food in at night and leave bait box in pen, even taking food in for period of day so squirrels would use the boxes would be ideal. Rats are everywhere and if you don't start with a management for them before you know it there will be 3, 4, 6 holes with estimates of a dozen rats per hole around your pen.