Out of the estimated six million to eight million dogs and cats entering animal shelters each year, 30 percent of dogs are reclaimed by owners compared to less than 5 percent of cats, according to the Humane Society of the United States (HSUS). The big difference? Cats tend not to carry identification.

“Cat owners are so averse to using ID tags, collars or other identification,” says John Snyder, HSUS vice president of the companion animal section. “Many cat owners say, ‘I never let them out,’ but anytime you open the door, you run the risk that your cat will get loose.”

Here are the pros and cons of some of the most popular identification methods and the potential health impacts.

Cat Identification No. 1: Microchips
A microchip, usually embedded between your cat’s shoulders, emits a code that a special scanner activates with radio signals. The scanner displays a unique ID that can be used to access ownership information from a database.

  • Pros: Microchipping is one of the favored forms of pet identification by veterinarians. It’s relatively inexpensive, ranging from $30 to $40. “For all practical purposes, it’s permanent,” explains Dr. Bonnie Beaver, a veterinarian and past president of the American Veterinary Medical Association (AVMA) who now teaches at Texas A&M University.
  • Cons: The information is not visible to a neighbor or other person who finds your cat. Identification can only be made with a scanner.
  • Risks: Endorsed by the U.S. Department of Agriculture in 2007, no conclusive health risks have been associated with microchipping, says Beaver. The AVMA says studies of four million chipped pets found less than 400 adverse reactions, the most common of which was that the chip moved from its original site. Studies suggesting a link between microchips and cancer in rats and mice have largely been discounted by the AVMA, given the differences in chip sizes and species.

Cat Identification No. 2: Collars and Tags
Getting your cat to wear a collar with a small tag featuring your name and phone number or information from a pet registry, is one of the best and cheapest forms of cat identification. Tags need to be updated if you move or change phone numbers. Some municipalities require tags to prove a cat is vaccinated against rabies.

  • Pros: “We think external collars and tags save more lives and prompt more returns than anything else,” says Snyder. “Anyone who finds a cat with a collar or tag can affect a return by calling the number on the tag.”
  • Cons: Collars can be removed, either deliberately or by accident. Tags can also get detached.
  • Risks: Collars can get caught on branches or brush outdoors, and on furnishings indoors. This can lead to strangulation or other injuries. Beaver recommends a breakaway collar, which is designed to break or open if pulled with a little force.

Cat Identification No. 3: Tattoo
One of the oldest methods of cat identification, tattooing is used more rarely to ID cats these days. Tattoos are usually applied inside the ear. Some countries use a standard tattoo symbol to indicate a cat has been neutered.

  • Pros: This is another permanent method of ID. It’s seen easily, without a scanner.
  • Cons: People aren’t accustomed to look for tattoo IDs. If they find one, says Beaver, they may not know what the number stands for or where it was issued.
  • Risks: Applying a tattoo can be painful, and it’s usually done under anesthesia. Short-term bleeding or scabbing may occur.

Cat Identification No. 4: Ear Notching
Ear notching — or ear “tipping” — involves the physical removal of a small portion of one of a cat’s ears. This is most often used by feral cat management programs to ID cats after neutering, says Beaver.

  • Pros: Ear notching provides a visual way for animal control to determine which cats have been neutered so they don’t have to round them up.
  • Cons: This is not a good ID method to trace a pet’s ownership, because it doesn’t list the owners’ information.
  • Risks: The procedure can cause temporary pain and blood loss.

Prevention, however, is the best method to prevent a
lost kitty. Beaver concludes, “Generally speaking, we recommend you keep
cats indoors.”