Normally when dogs can’t bark it is due to a medical reason and some dogs are bred to be quiet but, in this instance, this cute dog, a silky terrier, appears to have inherited a genetic defect which prevents him from barking and howling et cetera. He is incredibly cute. A lot of people would like a dog that cannot bark! Although I’m sure he has got used to it. It is not conducive to his welfare.
Two useful tags. Click either to see the articles: Speciesism - 'them and us' | Cruelty - always shameful