A real zoo I went to recently has a walk-in deer habitat with food dispensers to feed the deer with. We already have guest gates but I think food dispensers would be a fun idea and way to earn a little more income. It could also help to deter guests from feeding them food made for human consumption. It could work for only certain species (example: lets you feed deer and peafowl, doesn't let you feed lions and gorillas) and let you select which specie a certain machine is for. I imagine it'd also contribute positively to guest happiness.