Why does my boy dog have 8 nipples?

it’s probably a girl.

The same reason men have nipples.

Boys and girls of the same species are basically variations on the same body shape. Just like men and women both have two nipples, boy and girl dogs will both have the same number too.

All male mammals have nipples because the embryos all start out female, and some of them develop into males later. But they do that after the nipples have formed. Dogs have eight because they have more puppies at once than people have babies.

downtide is correct that dogs, like humans, develop nipples. On dogs, the count varies. I’ve read and have had friends say that their dogs have anywhere between 6 to 12, whether male or female.

As others said ..just because the dog is male doesn’t mean it won’t have nipples. Dogs are mammals ..therefore they have nipples, no matter the sex. And, yes…the more babies a species is prone to having at one time, the more nipples that species has (as a general rule).

I’m thinking your vet thought you were prank calling them.