Animal shelters quickly become overrun when residents of a city drop-off their unwanted pets during closed hours. One such pet is Shadow, dropped off in a box one snowy night outside an Iowa shelter. Shadow chewed a hole in the box to escape, and was found by shelter personnel the next morning shivering on a nearby fence. There are limits to the number of adoptable animals a shelter can house, and shelters with too many animals face closure by the Humane Society. Staff at the Iowa shelter recommend residents use Petfinder.com to find a shelter with available space.