How Come Small Dogs Live Longer Than Big Dogs?

Question

Why is it that my dogs, which weight about 15 pounds each, have a life expectancy of 14 or 15 years but a dog that weights nearly 100 pounds would have a life expectancy of maybe 8 years?

Answer 1

It's certainly true that very large dogs tend to come with more health problems because their bodies simply can't take the strain of their size - Great Danes and St Bernards and the like are simply 'too big'!!

However if you compare dogs to every other species of animal in the world, it actually makes no sense whatsoever that they live longer the smaller they are, even though we know they do. Think about it; huge elephants live for years and years, and the bigger the species of tortoise the longer its life expectancy. In comparison, little rodents only live for a few years, and bugs sometimes only for a day! Large animals have slower metabolisms which usually works in their favour.

Dogs are a complete enigma in this respect when compared with the rest of the animal kingdom - the only other exception being some birds which can live for 80 years or more.

Have a look at this article on body size, energy metabolism and lifespan, very interesting - the first line is 'Bigger animals live longer' and then goes on to explain why - doesn't explain why this doesn't apply to dogs!
http://jeb.biologists.org/cgi/content/full/208/9/1717

The only explanation I can think of is that given the huge variation of size we've created among domestic dogs, there's obviously an 'ideal size' for the basic canine design. You'd think it would be medium/largish dogs i.e wolf or wild dog size, but apparently by creating small dogs we've created the ideal canine size!

Also keep in mind that dogs can be TOO small - very tiny ones like teacup chihuahuas tend to have a myriad health problems that shorten their lifespan. They're not supposed to be THAT small.

VERY interesting q by the way, nice one!

Chalice

EDIT: OK a vet at work has a theory concerning the relative size of dog's hearts. Great Danes may have a body mass ten times that of a Jack Russell, but their hearts are certainly not ten times as big - they're maybe two or three times as big! Ergo, large breeds simply do not have large enough hearts to support their size for any length of time; they're bound to fail a lot sooner.

Answer 2

This Site Might Help You.

RE:
How Come Small Dogs Live Longer Than Big Dogs?
Why is it that my dogs, which weight about 15 pounds each, have a life expectancy of 14 or 15 years but a dog that weights nearly 100 pounds would have a life expectancy of maybe 8 years?

Answer 3

There are alot more things that can go wrong in large breeds' bodies- like hip, muscle, heart, etc. problems. It's because their bodies have alot more strain put on them than small dogs. It's kind of like comparing the life expectancy of an average person and an obese person. There's just alot more strain put on the body when there's more weight added.

Answer 4

From what I understand, a bigger dog's large, heavy frame is harder on them than a small dog's. (It may be harder on their hearts, too, since the heart would work harder to pump blood further). It could also be because smaller dogs live indoors more and mostly live lives of leisure, while bigger dogs are more likely to be outside or "working" dogs.

Answer 5

big dogs are under more strain, their joints, their hearts.

my friend has a jack Russel who is 22yrs old, shes the oldest dog iv known, although shes not the oldest dog ever.
your right, small dogs such as terriers make about 16 or more, while great Danes have a life expectancy of only 8-10 years.
it also depends on breed, some small breeds such as the cavalier, are known to only make 11yrs, mainly due to bad breeding, but i know of plenty of cavs whom are over 13, and looked after a 17yr old one. also looked after a 18yr old GSD

Answer 6

usually small dogs don't live longer than large dogs because they have more health problems