Olfactory stimulation induces filial preferences for huddling in rat pups

Rat pups of all ages huddle with conspecifics, but the senosory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present experiments indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in pups from both scented and nonscented litters. Pups from scented nests preferred to huddle with a scented stimulus rat, whereas control pups preferred a nonadulterated rat stimulus. Additional testing indicated that the affiliative preferences were specific to rearing odor and were not based on decreased aversion to test scents, or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation.