Polanco, A., Meagher, R., Mason, G. 2021. Boredom-like exploratory responses in farmed mink reflect states that are rapidly reduced by environmental enrichment, but unrelated to stereotypic behaviour or ‘lying awake’. Applied Animal Behaviour Science 238, 105323.

Consistent with boredom, prior work has found that mink raised in non-enriched (NE) or enriched (E) conditions differ in their motivations to seek stimulation: NE mink spent more time oriented towards and in contact with diverse stimuli presented to them (ranging from rewarding to aversive), and in one study, NE mink showed shorter latencies to contact these stimuli and consumed more treats (Meagher and Mason, 2012; Meagher et al., 2017). Here, in Study A, we used a new population of young adult males (n = 30) to test the hypothesis that this reflects boredom-like states rather than long-lasting traits, being rapidly reversed by access to more stimulating environments. Minks’ exploration of stimuli was tested after seven months in minimally enriched control cages (containing a wiffle ball and shelf), and re-tested a median of six days after half the mink were moved to larger cages that were enriched with rewarding items. Although latencies to contact stimuli (F1, 27.42 = 0.23, p = 0.32) and proportion of treats consumed (F1, 27.45 = 0.44, p = 0.26) were not reduced by access to enriched housing, contact durations were (F 1,29.11 = 14.23, p = <0.05) and orientation times tended to be (F 1, 29.22 = 2.37, p = 0.07). Boredom-like exploration in farmed mink thus reflect states that are rapidly reduced by environmental enrichment. Enrichment-access also significantly reduced stereotypic behaviour (SB; z = 3.81, p = <0.05), although lying awake (another potential boredom-like indicator) unexpectedly increased (z = −4.15, p = <0.05). However, the reduction of SB did not correlate with reductions in exploration (F1,12 = 0.73, p = 0.41), indicating that SB and boredom-like states are independent. In Study B, we pooled data from all three populations studied to date, to re-test all hypotheses with greater power (N = 79). This revealed no significant associations between exploration of stimuli and SB, nor with lying awake. Furthermore, only contact and orientation durations were consistently lower in enriched housing (F1,72 = <45.50, p = <0.05), suggesting that these measures are most sensitive to motivations to seek stimulation. Overall, Study B shows that baseline time-budgets of SB and lying awake cannot reliably be used to identify boredom-like states in mink. However, Study A supports the hypothesis that increased exploration of diverse stimuli by captive animals in unstimulating housing reflects transient, reversible boredom-like states (not long-lasting traits).