Prenatal olfactory learning in the domestic dog

Prenatal chemosensory learning has been demonstrated in a wide variety of mammals, including humans, sheep, rabbits, rats and mice, and it may help to shape development and behaviour. The domestic dog, Canis familiaris, is renowned for its olfactory acuity. Furthermore, it belongs to an order of mammals (Carnivora) for which there has been no evidence of prenatal learning. We examined how prenatal exposure to a chemosensory stimulus (aniseed), via the mother's diet, affected the chemosensory preferences of neonatal pups. Pups received two-choice tests of aniseed versus water and vanilla (a novel odour) versus water. Twenty-four-hour-old pups exposed to aniseed during gestation preferred aniseed more than did pups not exposed to this odour (experiment 1) but showed no preference for vanilla over water (experiment 2). Thus, the preference was specific to the stimulus experienced in utero. Pups tested 15 min after birth showed a similar preference for aniseed (experiment 3), thus ruling out the possibility that postnatal exposure influenced the preference. The results indicate that prenatal chemosensory learning is present in the Carnivora and suggest that such learning may be present in all mammals, serving an important function in early mammalian development.