Check for an owner first: ear tip, microchip scan and a found report. Then ask your shelter how to keep it legally, and see a vet before it meets your other cats.
Rule out an owner before you get attached
Do three things before you start thinking of the cat as yours: look for an ear tip, get a microchip scan, and file a found report with your local shelter. The cat may have a home a few doors away, even if it looks thin. Once those are done, phone the shelter or animal control and ask how to keep a found cat legally in your area, because the answer varies. Then take it to a vet and keep it apart from your own cats until you have results. Do not rename it, change a chip or post it as adopted during this stage. This is general information, not legal advice.
Why the cat may not be free to keep
Pets are usually treated as someone’s property, and that does not change because you fed one. San Diego County says a pet is considered personal property, that you cannot keep a stray animal, and that pet owners can press criminal charges against someone who keeps their animal. Its cat section says that a person who wants a found cat can ask for a Finders’ Hold, which puts them first in line if no owner claims it. Oakland, California, says you cannot adopt a found pet until you have tried to locate the owner and the stray hold is over. Other areas take a much lighter approach, and many agencies do not take in healthy outdoor cats at all. Ask, and write down the answer.
Check ears, collar and chip
A flat, straight edge on one ear usually marks a sterilized community cat. Best Friends Animal Society says to leave ear-tipped cats who appear healthy right where they are, and such a cat often has a caretaker who feeds it. So do not take it in without talking to that person. Check any collar, including the inside of the band. Then put the cat in a carrier and get it scanned. Best Friends says most vets and pet supply stores will do this at no cost, but call first. Humane World for Animals, formerly the Humane Society of the United States, says a local rescue may be able to lend you a scanner if you cannot move the cat. See our post Found a cat with a collar but no tag: what to do next.
Look properly, and keep a record
Humane World sets no fixed time for an owner search, and neither do most agencies, so ask yours. Do the full list anyway: ask neighbors and mail carriers, file a found report with area shelters, post flyers nearby, and post on Nextdoor and local Facebook groups. Search lost cat posts as well, because you may find the owner there first. Keep dated screenshots and photos of your flyers. In the Huang study of 1,210 missing cats, published in 2018, cats found alive had a median distance of about 165 feet from where they escaped. That was an online survey, so treat it as a guide, but start at the nearest doors. In the same study, only half had been found alive by day 30, so an owner may still be looking weeks later.
See a vet early
Book a general exam, and say the cat is a stray with an unknown history. Cornell’s Feline Health Center recommends testing all cats for feline leukemia virus, FeLV, before bringing them into a home. It also says a cat’s FIV status should be determined when it is first acquired, even if it will live alone. If exposure was possible and the first FIV test is negative, Cornell says retesting after at least 60 days gives a more accurate result, because antibodies take time to develop. Ask your vet about rabies vaccination, parasites, whether the cat is already spayed or neutered, and what your state requires. The vet will decide what the cat needs. Keep the receipts, as they show the care you have given.
Keep it apart from your own cats
Set up one closed room with food, water, a litter box and somewhere to hide, and keep your other pets out until your vet says otherwise. Cornell says FeLV spreads through close contact, including bite wounds, mutual grooming, and shared bowls and litter boxes. It says FIV spreads mainly through bite wounds. Humane World advises bite-resistant gloves when handling an unfamiliar cat. If you are bitten or scratched, the CDC says to wash the wound right away with soap and water, and to get medical care urgently if you may have been exposed to rabies.
If the owner turns up
Be ready for this, even after weeks. Ask for something only the owner could know, such as a mark you left out of your post, and for a photo of the cat at home. If it checks out, the honest step is to give the cat back. If you are worried about how it was treated, call animal control and let them look into it. Do not keep the cat on your own judgment. Paying the vet bills and buying a chip does not settle ownership. In Finn v. Anderson, a 2019 City Court case in New York, a couple fed a cat for months, paid for care and had it chipped, and a neighbor still won in what the court called a very close decision.
Make it official
When the agency says you may keep the cat, get that in writing. If you adopted through a shelter, keep the contract. If the cat has no chip, ask your vet to place one and register it in your name. If it has a chip in someone else’s name and the agency has cleared you, ask the agency or the registry how to change it. Have the cat spayed or neutered if it is not already, and get a license if your area requires one for cats. Finally, take down your flyers and close your found reports, so nobody keeps searching for a cat that has a home.
Sources
San Diego County Animal Services: sandiegocounty.gov/content/sdc/das/lost-found/found.html. Oakland Animal Services: oaklandca.gov/Community/Pets-Animals/Lost-and-Found. Best Friends Animal Society: bestfriends.org/node/572187. Humane World for Animals: humaneworld.org/resources/how-help-stray-or-found-cat. Cornell Feline Health Center, FIV: vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-immunodeficiency-virus-fiv. Cornell Feline Health Center, FeLV: vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-leukemia-virus. CDC, rabies: cdc.gov/rabies/about/index.html. Huang et al., Animals, 2018: pmc.ncbi.nlm.nih.gov/articles/PMC5789300. Finn v. Anderson (2019): animallaw.info/case/finn-v-anderson.