* No Central Registry: There's no global database tracking every pet and their fur status.
* Varying Definitions: What counts as a "pet"? The term includes a wide range of animals, from cats and dogs to hamsters and fish.
* Fur vs. Hair: The difference between fur and hair can be subtle, and some animals may have both.
* Constantly Changing: The number of pets worldwide is constantly changing as people acquire and lose pets.
Instead of a number, we can say:
* A vast majority of popular pet mammals have fur, including dogs, cats, rabbits, hamsters, guinea pigs, and many more.
* Some common pets like birds, reptiles, and fish do not have fur.