In the wild animals never die of old age in our sense. If an individual can't defend his life without assistance, it quickly perishes, as a rule. When the human comes to protect and takes on his own search for food and protection from predators and diseases, the lifetime may increase.
The dog's existence is closely connected to people and a young puppy soon becomes the member of a pack, a family, as we'd say. But a dog grows old faster than a man and the owner desperately starts to count how long his pal will hold out. One will hardly refrain from comparing a dog and a human age. At first, a one year of dog life equated to 4 to 5 years of a man's life. The error of such arithmetic was large, especially as concerned to the two first years of the animal's life. The more accurate is when you convert the first year of dog life into 14, the second year - into 7, and each of next years into 5 years. Thus, the three-year-old dog in his prime is like a 26-year-old man (not the 12-15 teenager as you can get using the first scheme). The 10-year-old dog may be regarded as a 61-year-old man, and at 15 he would be an elder of 86 years. But here are some fine points: the domestic animals that belong to the same species but different breeds have different lifetime. Small-breed dogs as well as little mongrels can easily live up to 14 years, but a large-breed 10-year-old dog can be considered a long-liver. Most of Great Danes can hardly get over the 8-years point. The individual lifetime is also very different. The veterinarians say that in the course of their practice they met 18 and even 20-year-old dogs. All of them belonged to small or middle-sized breeds (these are apparent long-livers).
As one can see, we are able to help our friends to realize the highest possible, according to their genetics, lifetime. At this, their real life becomes one and a half or even twice longer.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).