Kennel club registrations have been used in a number of studies to estimate ownership levels and fashion trends among dog breeds. They cannot, however, give a complete overview of the contemporary trade in pet dogs, and additionally, may be particularly poor at monitoring trends among some welfare-vulnerable breeds. Here, we compared data from online advertisements for the UK sales of single-breed dogs over an 18-month period, with equivalent data (including for prior and subsequent years) from the UK Kennel Club. Kennel Club registration rates and breed popularity rates online were positively correlated. However, some breeds, including the Jack Russell terrier, Border collie and Chihuahua were considerably over-represented in online advertisements when compared with Kennel Club registrations, indicating a hidden market for certain breeds. In addition, the online dataset provided information on the sale and re-homing of adult dogs, showing high rates of adult homing of the Staffordshire bull terrier, Siberian husky and Rottweiler. We conclude that online pet-sales websites are an important and complementary source of data about the market in, and popularity of, a wide range of dog breeds.
Keywords: Dog; brachycephalic; breed; pedigree; welfare.