It is interesting to note how little difference there is in actual birth weights from one breed to the next in respect to what weight at full maturity will be. The average Chihuahua's birth weight is approximately three to five ounces while the Great Dane's is normally four to five times that. But stop to consider the weight of the two breeds at maturity. The well-bred Chihuahua matures at a maximum of 6 pounds and the Great Dane tops the scales well past 100 pounds. Note that the rapid growth experienced by the Great Dane on its relatively short journey to maturity takes a heavy toll on the breed's physiology and longevity. A Chihuahua might live well into its teens, but six to seven years is considered the average life expectancy of the Great Dane.