Denna sida på svenska. We often hear that the lifespan of the rat has become shorter and shorter through the last few years here in Sweden. Just a few years ago it was rather common that rats lived came to live for over three years, but today more and more rats live for only 1 1/2 years. How can this be? Exactly how this has happened nobody knows, and it is easy to blame the Mykoplasma infections that practically all pet and fancy rats in Sweden today are infected with, but I am planning to point to towards a few other reasons in this article. This may be the right place to point out that a Mykoplasma infection does not automatically have to end the rat's in advance.
There is a clear tendency that pure pet rats live longer than the breeding stock belonging to various rat breeders throughout the country. This is not so strange since it is easier to get infected by various diseases for the rat that lives together with several other rats.
One point that many a person still has not succeeded to understand is that strong inbreeding usually leads to more short-lived animals, this fact can't be ignored. Of course it is fully possible to create a line of inbred animals where all animals have extra long livespans (I can't understand nodody has done that yet!) if you concentrate on the trait lifespan, but the normal way to breed tame rats in Sweden is to breed for appearance. This way you will sooner or later breed rats with prettier looks, but all other traits will soon deteriorate, like lifespan and general health status.
Besides, it is highly convenient for the big breeder if the rats do not live too long, so they do not have to fed for so long.
Another important detail that nobody ever even seem to have heard of is that the breeding of mainly young animals has been scientifically proven to impede longevity, this in combination with inbreeding makes a greater effect. This is actually rather easy to understand. If you mainly breed from young animals you will have moved forward a few generations already before you can discover that several of the animals in your breeding stock die young or aquire various diseases.
To counteract this you ought to breed from older animals. Females can not be bred after a certain age but an old male in good condition should be considered highly valuable and be used rather than a younger male. This means that either the breeders has to keep a bunch of older males for breeding purposes or that the breeders place the best males as pets, with the option to let the male meet a few females once in a while.
This of course a question of money! A breeder whose animals in general do not live for more than 1 1/2 year has fewer animals in his or her rattery, breed the animals earlier and reaches show results faster since this breeder can produce more generations in a shorter period of time. Furthermore this breeder can sell new rats more often since these rats don't live as long. This means that this breeder gains more money from the rattery in the short-term sence.
The question is: is this how we want our rats?
Written by Eva Johansson in 1994 - 1995.
Copyright Eva Johansson.
Last update: 11th of August 2006.