Behavioural and physiological differences between silver foxes selected and not selected for domestic behaviour
The degree of domestication of an animal is difficult to estimate because the animal's phenotype depends not only on its genetic make-up but also on its experiences during ontogeny. In addition, comparisons between wild and domestic animals suffer from the lack of a proper reference
population. In this study, we compared the offspring of silver foxes (Vulpes vulpes) that had been selected specifically for tameness for more than 30 generations (NOVO) with normal Finnish farmed foxes (FIN) and with reciprocal hybrids between these two strains. All animals were housed
under standard farm conditions without any extra handling. The NOVO foxes had higher domestication indexes and lower fearfulness scores than the FIN foxes, with their hybrids showing values in between. Almost all NOVO foxes started eating in the presence of a human and took a titbit from him,
whereas only a few FIN foxes did so. Open field and urinary cortisol tests failed to discriminate between the genotypes. The NOVO cubs had lower levels of serum cortisol both before and after a stressful situation or ACTH injection and showed lower stress-induced hyperthermia than the FIN
cubs, with the hybrids showing results in between. NOVO foxes can be used as a reference when developing and validating behavioural tests for use in the selection of less fearful silver foxes. The observed low fear levels and low stress hormone levels suggest better welfare in the NOVO foxes
under standard farm conditions.