Serum Levels of Cortisol and Testosterone in American Mink (Neogale Vison) Selected for Aggressive and Tame Behavior towards Humans

Abstract

Several molecules, including glucocorticoids (cortisol, corticosterone, etc.) and testosterone in mammals, are thought to be associated with tame/aggressive behaviour towards humans, but these relationships remain controversial. The American mink (Neogale vison) represents a model in the studies of physiological traits in aggressive and tame behavioral phenotypes. Given the seasonality in reproduction, fur moulting, and hormonal levels during the life cycle of mink and the reciprocal relationships between the hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal axis, it is necessary to study the levels of cortisol and testosterone in the behavioral phenotypes of the animals in various seasons. Of particular interest is the period after the breeding season (late March—early April), when the level of androgens decreases. The aim of the study was to characterize the neuroendocrine physiological phenotypes associated with aggressive and tame behaviors by measuring the levels of cortisol (basal level) and testosterone in the blood serum of American mink at the end of the breeding season. Blood samples were taken from animals selectively bred for tame and aggressive defensive reaction towards humans at the Institute of Cytology and Genetics in Novosibirsk, Russia. No differences were found in serum levels of cortisol and testosterone between aggressive and tame mink. We found a significant negative relationship between the studied hormones in tame mink. Thus, selection of American mink for either aggressive or emotionally positive responses to humans does not appear to be associated with changes in the levels of the hormones studied at the end of the breeding season.