Latin America's Pet
The spread of the popularity of the Chihuahua north to northern Mexico and south to South America is widely attributed to the arrival of the Spanish conquistadors in the early 1500s. According to this theory, the Spaniards not only took these dogs with them as they conquered and pillaged, they also brought back Chihuahua-like dogs to Europe.
Some dog historians contest this theory. These researchers claim that the more likely result of the Spaniards' exploration and presence was the near decimation of all domestic dogs existing at the time. Upon their arrival, conquistadors enslaved the Aztec people. Aztecs, along with many other older civilizations, raised dogs not only for religious reasons and as pets but also for food.
Another theory is that Spaniards brought black-and-tan terrier-type dogs with them and that this dog interbred with the Tolchichi to develop into today's Chihuahua. Though one would think that only the bare essentials would have been onboard the Spanish galleons that were already loaded with men, horses, and supplies, a rat-killing terrier might have been of benefit onboard ships noted for rodent infestations.
Dogs raised for consumption, of course, were raised as livestock — typically larger in size, neutered, and fattened up with corn. The Aztecs had no need to eat their smaller dogs, which wouldn't have made much of a meal anyway. Under the cruel servitude of the Spaniards, however, the Aztecs were no longer in a position to raise these smaller dogs strictly as a luxury and religious item. Faced with starvation, the Aztecs could have turned to their revered, smaller dogs for survival.
The Spanish conquistadors likely turned to dog as a common meal during food shortages, too. Armies of conquistadors (whose horses required grain and depleted this source of food) are attributed with not only wiping out entire native civilizations from Florida through Mexico and into Central America, but also with raiding Indian tribes' camps for thousands of domestic dogs, whether they were raised as working dogs, a source of food, or as religious and luxury items.