Maternal temperament modulates curiosity and cortisol responses in farmed mink

Early life events can shape the development of individual behavior and stress sensitivity. This study explored whether the temperament of the mother modulates curiosity, fear, and Hypothalamic-Pituitary-Adrenal (HPA)-axis hormones in different lines of mink. We designed a study with all combinations of cross-mating between males and females from lines of Confident (C) and Fearful (F) mink. The offspring (N = 600) were cross-fostered by C or F mothers until weaning after 1.8 months. Fearfulness and exploration in three behavioral tests plus plasma ACTH and cortisol were measured in the 6-9 months old offspring. Mink of confident parents (line CC) were consistently more curious, the mixed (CF, FC) showed intermediate reactions, and mink of fearful parents (FF) were the least curious and most fearful in all tests. A higher proportion of the offspring was curious when raised by a C foster mother, regardless of the genetic origin (stick test: 45.1% vs. F foster mother: 34.5%). Cortisol was influenced by line of the biological mother, but not by the sire or by the foster mother; offspring of C dams (CC, CF) had consistently lower cortisol concentration (P < .001) than offspring of F dams (FF, FC) in response to acute stress. In conclusion, besides the selection lines (inheritance from both parents) being a major factor determining curiosity/fearfulness of mink, the confident foster mothers increased offspring curiosity. Additionally, we found maternal effects on the HPA-axis, leading to a higher cortisol response to acute stress in adult mink offspring gestated by fearful mothers. The results add to the existing knowledge on maternal influence on offspring development and are particularly relevant for on-farm welfare where selection for low-fear and explorative dams can decrease offspring fearfulness and stress responses.