Many apartment complexes and rental homes institute no pet policies. No pet policies are a leading cause of animal abandonment, which is considered a crime in many jurisdictions. In many cases, abandoned pets have to be euthanized due to the strain they put on animal shelters and rescue groups. Abandoned animals often become feral or contribute to feral populations. In particular, feral dogs can pose a serious threat to pets, children, and livestock.[51] Feral cats are known to hunt endangered birds and have interbred with wild cat populations.