They probably have lots of holes; they are just really good at concealing them! In order to quickly escape from predators, chipmunks build multiple entrances to their burrow system. If chipmunks have taken up residence in your yard, it means that they have found all that they require for survival: food, water, shelter, and space. Chipmunks are omnivores, which means that they eat both plant and animal material. They are known to eat seeds, nuts, fruits, insects, meat, and bird eggs. There is no need to supplement their feeding. In fact, biologists do not recommend supplemental feeding. It can lead to higher populations than an area can naturally handle, which can eventually cause disease issues and population reductions. If you have pets that go outdoors, I would recommend keeping them out of that part of the yard. Otherwise, sit back and enjoy! Thanks for the question.