Domesticated silver fox
 |
Tame Silver Foxes are the results of nearly 50 years of experiments in Russia to domesticate the silver fox. Notably, the foxes did not only become more tame, but more dog-like as well: the new foxes lost their distinctive musky "fox smell", became more friendly with humans, put their ears down (like dogs), wagged their tails when happy and began to vocalize and bark like domesticated dogs. The breeding project was set up by Russian scientist Dmitri Belyaev, encouraged by the Communist Party of the time because of its link with the aim to control and improve the human condition.
Initial experiment
Scientists were interested by the topic of domestication, and how wolves were able to change and "improve" to become tame, like dogs. They saw some retention of juvenile traits by adult dogs: both morphological ones such as skulls that were unusually broad for their length, and behavioural ones such as whining, barking and submissiveness.
Belyaev believed that the key factor selected for domestication of dogs was not size or reproduction, but behaviour; specifically amenability to domestication, or tamability. More than any other quality, Belyaev believed, tamability must have determined how well an animal would adapt to life among human beings. Because behavior is rooted in biology, selecting for tameness and against aggression means selecting for physiological changes in the systems that govern the body's hormones and neurochemicals.
Belyaev decided to test his theory by domesticating foxes; in particular the Russian Silver Fox. He placed a population of them in the same process of domestication, and he decide to submit this population to a strong selection pressure for tamability.
Now, Russian scientists have a number of tame foxes which are fundamentally different in temperament and behaviour from their wild forebears. Some important changes in physiology and morphology are now visible, such as mottled or spotted colored fur.
Project today
Following the demise of the Soviet Union, the project has run into serious financial problems. In 1996 there were 700 tame foxes, but in 1998, without enough funds for food and salaries, they had to cut the number to 100. Most of their expenses are covered by selling the pelts, but they remain in a difficult situation, looking for new sources of revenue from outside funding.
On November 22, 2005, the journal Current Biology published an article about the genetic differences between the two fox populations: Jazin et al.: "Selection for tameness has changed brain gene expression in silver foxes." Current Biology, Vol. 15, R915-R916, November 22, 2005, DOI 10.1016/j.cub.2005.11.009 In this study, microarrays were used to detect differential gene expression between tame foxes, non-tame farm-raised foxes, and wild foxes; one set was raised at the same farm as the tame foxes, and the other set was wild. 40 genes were found to differ between the tame and non-tame farm-raised foxes, although about 2,700 genes differed between the wild foxes and either set of farm-raised foxes. The authors did not analyze the functional implications of the gene expression differences they observed.