Most people who call about feral cats complain that the cats are living under a deck or porch, making noise, fighting, or stealing pet food left outside. Many of these people have a genuine concern and care for these animals, and don't like seeing the population getting out of hand. Some people even begin to feed feral cats, and soon find that they are swarmed by hungry felines looking for a free handout.
Stray cats will leaving droppings and urine in the areas they live, and will of course scratch and dig. Stray cats are a source of fatal and non-fatal diseases transmittable to humans and domestic cats, including rabies, ringworm, toxoplasmosis, cat scratch fever, allergies, feline leukemia, feline distemper and secondary bacterial infections.