There are three main reasons why trapping does not work: the vacuum effect, the availability of resources, and nature's ability to adapt.   The Vacuum Effect:   Trapping and removal of wildlife has proven to be ineffective. One of the main reasons is called the vacuum effect, which is simply when you remove an animal, then the next night another animal takes its place. A 20-year study of urban coyotes by The Ohio State University of the Chicago area in Cook County, Illinois demonstrates the effect of removal of wildlife. Learn more about the Urban Coyote Research Project Study Results.   The Availability of Resources:   The availability of resources is another reason wildlife may be in your neighborhood. Dallas has a very healthy urban ecosystem. Not only do parks, streams, and greenbelts make great habitat, but some backyards do too. Areas underneath sheds, decks, or brush make great homes for many of our wild neighbors. Bird feeders, uncovered trash, vegetable gardens, or pet food that has been left outside provide food for many species.   Nature's Ability to Adapt:   Research has found that wildlife will adapt when resources are available in a habitat. Litters are bigger, more of the offspring survive, and the numbers return to normal within a year or less.   “Wild Furbearer Conservation and Management in North America (Novak et al, 1987) provides data demonstrating that when raccoons exhibit low reproductive rates, as much as 49% of the population can be trapped out and they will rebound back to their former level by the next breeding season. When raccoons exhibit high reproductive rates (typical with an ongoing trapping program), as much as 59% of the population can be trapped out and the population will replace itself by the next birthing season. A similar scenario has been observed among coyotes and groundhogs.”   Raccoon Density and Movements After Population Reduction to Control Rabies Article with Citation