Human-socialized dogs and wolves show similar behavioural reactions to human fear odour.

Past studies show that dogs react to human fear odour with avoidant but individually variable behaviours, yet it remains unclear whether this response is an effect of domestication or an ancient trait. We tested similarly raised, human-socialized dogs and wolves, comparing their reactions to human fear versus neutral odours. Using a within-subject design, animals were asked to choose between two targets: either both containing neutral human samples (Control condition) or one neutral and one fear sample (Experimental condition). While neither showed a preference for the fear or neutral smell, both dogs and wolves spent less time near the targets, looked more at the handler, and refused a choice less frequently in the Experimental condition, when the fear scent was present, compared to the Control (when it was absent). Additionally, dogs, but not wolves, were more likely to end the session prematurely in the Experimental condition compared to the Control. Finally, neither species showed greater individual variability in one condition compared to the other. These findings indicate that, like dogs, wolves alter their behaviour in response to human fear odour if they have the same life experience, suggesting a sensitivity that may precede domestication.