Most wildlife species have the potential of becoming a nuisance. Whether or not a species becomes a pest can be directly correlated to the degree at which that animal can be tolerated by humans. For many people, squirrles feeding in their yards or gardens is not a problem; while at the same time, a neighbor may feel the squirrels are a complete nuisance. Common wildlife pests include squirrel, raccoon, skunk, mice, coyote and pigeon. Wildlife species are usually only pests in certain situations, such as when their numbers become excessive in a particular area. Human change in the environment will often result in increased numbers of a species. For example, piles of scrap building material make excellent sites for rodents to frequent, called harborage. Food left out for household pets is often equally attractive to some wildlife species. In these situations, the wildlife have suitable food and habitat and will usually become a nuisance. Trapping may become necessary to remove these nuisance animals.