From GT New Horizons

Animal Traps

Animal traps must be touching grass on four sides, and one of those must also touch grass. One of the Bait types needs to be placed in the left slot. Periodically one bait will be consumed and a potential drop for its type generated into the inventory. No animal actually needs to be present. Three meat types, Raw Rabbit, Raw Turkey and Raw Venison, are exclusive to traps. Animal traps cannot be automated with Hoppers - hoppers won't interact with the top or sides, and will pull bait out of the bottom.

Item Fruit Bait Grain Bait Veggie Bait
Bone 9% 9% 9%
Egg 9% 9% 9%
Feather 18% 18% 18%
Leather 9% 9% 9%
Raw Beef 9%
Raw Chicken 27% 27% 27%
Raw Mutton 9%
Raw Porkchop 9%
Raw Rabbit 27%
Raw Turkey 18%
Raw Venison 9%

Fish Traps

Fish traps only need to be touching water on four sides.