 Public attitudes towards feral cats vary widely , ranging from seeing them as free @-@ ranging pets , to regarding them as vermin . One common approach to reducing the feral cat population is termed ' trap @-@ neuter @-@ return ' , where the cats are trapped , neutered , immunized against rabies and the feline leukemia virus , and then released . Before releasing them back into their feral colonies , the attending veterinarian often nips the tip off one ear to mark it as neutered and inoculated , since these cats may be trapped again . Volunteers continue to feed and give care to these cats throughout their lives . Given this support , their lifespans are increased , and behavior and nuisance problems caused by competition for food are reduced . 
