Maternal Care Can Rapidly Induce an Odor-Guided Huddling Preference in Rat Pups

Olfactory-guided huddling is learned and expressed by postnatal day (PND) 15, when rat pups huddle preferentially with conspecifics or with targets bearing an odor previously associated with maternal care. Experiment 1 replicated this induction of an odor-guided huddling preference with a truncated regime of conditioning with a scented foster dam. Pups exposed to an odor in association with foster maternal care during five daily 2-hr sessions on PNDs 1-5, 5-9, or 10-14, but not pups merely exposed to the odor, displayed a huddling preference for the conditioned odor, but only when conditioning commenced after PND5. Experiment 2 demonstrated that a single, 2-hr exposure to a scented foster dam can induce a huddling preference in pups. Analysis of maternal behavior during the 2-hr conditioning sessions on PND14 revealed that frequency of maternal hovering over pups, but not licking/grooming or duration of contact, was associated with induction of the odor preference. (C) 2008 Wiley Periodicals, Inc. Dev Psychobiol 51: 95-105, 2009.