Even if it probably wishes every dog owner, his beloved four-legged friend would reach a biblical age or at least live as long as a man, so this is an unrealizable wish. Because an average dog's life is unfortunately much shorter than an average human life. Most people surely know the (however strongly simplified) formula, according to which a "human year" should correspond to about seven "dog years".
A 10 year old dog would then be in about the same age state as a 70 year old human. This rule of thumb is however only very roughly applicable, on the one hand, because neither humans nor dogs age linearly, on the other hand, because the aging proceeds differently with the different dog races and it depends in addition very much on how a dog is nourished, maintained and medically cared for.
How old does the dog become on average?
Statistically, how long do dogs actually live and which dog breeds have the highest life expectancy? As a rule, smaller dog breeds live longer than medium-sized ones, and large dogs live for a much shorter time than smaller ones. Rehpinscher, Chihuahua or dwarf poodle, for example, have an average statistical life expectancy of 16 years, individual representatives of small dog breeds may well live to 20 years.
Medium-sized dog breeds such as spaniels, beagles and collies have an average life expectancy of 12 to 13 years, and very large dogs such as St. Bernards, Irish wolfhounds, German shepherds or Great Danes only live for about 6 to 8 years, statistically speaking. But of course these are only statistical values. Large deviations upwards or downwards occur again and again. If you look at the ancestors of today's dog breeds, the wolves, they are about the size of medium-sized dogs and their life expectancy is on average about 12 years, in captivity about 15 years.
What is the reason for the difference in life expectancy between dogs?
What is the reason that smaller dogs have a higher life expectancy than larger dogs is not yet completely clear scientifically. It is in a way even illogical, if one considers that in principle large animal species live longer than small ones. The elephant will normally live much older than the mouse, the horse older than the brown hare. But the different life expectancies of dogs do not concern the animal species dog per se, but the specific dog breeds. And there are very few animal species that differ so much from each other in size, weight and physique, depending on the breed, as dogs do. They can weigh 2 kg when fully grown, but also over 70 kg. The shoulder height can be 25 cm but also 80 cm and more.
On the other hand, if you look at the birth weight of puppies, a newborn Papillon (a dwarf spaniel), for example, weighs an average of 0.16 kg and a Great Dane puppy weighs an average of 0.74 kg. When fully grown, the Papillon weighs around 3 kg, but the Great Dane weighs 85 kg. So the dwarf dog multiplies its birth weight about 48 times, the Great Dane over 85 times.
The huge growth performance that especially large dogs have to accomplish in a short time is very likely the reason why they age and die faster. They need especially much energy to grow and at the same time also to maintain the function of all organs.
They might lack this energy to a certain extent in order to intercept the so-called free radicals that cause cell damage in the organism or also to be able to repair this cell damage again and again. That is why the aging process starts earlier and is steeper in large breeds. The life expectancy, i.e. the biological lifetime, is therefore reduced.
What else influences the life expectancy of dogs?
Of course, it is also determined by the attitude of the dog. Does he get healthy nutritious food, enough exercise, good care? Also the possibility to be able to intervene and support with effective medicines in case of diseases and organ damages has also a certain influence on the life expectancy.