The size of a Chihuahua's brain is relatively small compared to larger dog breeds, but it is proportional to their body size. On average, a Chihuahua's brain weighs between 1.5 and 3 ounces (or 42 to 85 grams), which is about 0.1% to 0.2% of their body weight.However, brain size alone is not a reliable indicator of intelligence. Many factors contribute to a dog's cognitive abilities, such as their genetics, training, and socialization. Chihuahuas are generally considered to be an intelligent and trainable breed, despite their small brain size.
