Hi. I'm Dr. Fiona Caldwell and I'm a veterinarian at Idaho Veterinary Hospital and I'm answering questions from pet owners today for Pets Best. This question is, "Why do small dogs typically live longer than larger dogs?" This is a great question and it's definitely very true. Your typical Great Dane or Mastiff really only has a lifespan of sometimes just seven to nine years, and Chihuahuas or Yorkies or your other little breed dogs, it's not uncommon for us to see them live over 15 years.
Studies have shown, research has shown that larger dog’s age faster. So, clearly they're not living as long because their bodies are aging quicker. Exactly why they age quicker isn't exactly known. But we suspect it has something to do with just their increased size causing more wear and tear. They have more cardiovascular output that's needed. They require more calories and their bodies just don't hold up as long.
Another added factor that can decrease pets' lifespan is obesity. Not necessarily the size of the standard breed of the dog, but just the size of the dog itself. We do know that a heavier pet tends to live on average one to two years less than their counterparts. So another reason to keep your pets lean.