In order for a naked bitch to bring live puppies at all, she must cover a furry dog and vice versa. Otherwise, disorders incompatible with life occur during the development of the fruits or the bitch does not deliver the puppies at all. Mating of purebred hounds (in all these breeds) is allowed in this connection: bare dog + hairy bitch and vice versa bare bitch + hairy dog. From such connections, both furred and naked puppies are always born in one litter. These are Peruvian hairless dogs, Mexican and still very popular Chinese Crested dogs. Baldness also brings with it poor teeth and other problems ... This is basically an artificially maintained natural anomaly. It's (I assume) the same for cats.