Housing pregnant mice (Mus musculus) in small groups facilitates the development of odor-based homing in offspring

Infant mice (Mus musculus) born to dams housed in isolation throughout pregnancy (IsoPreg) begin differentially approaching homenest bedding over clean bedding on Postnatal Day 6. Offspring of dams housed with 2 other potentially pregnant conspecifics (SocPreg) display such homing behavior on Day 4. Earlier onset of homing reflects facilitated olfactory responsiveness in SocPreg pups, rather than qualitative or quantitative differences in IsoPreg versus SocPreg nest odors, body growth, or motoric capabilities. Exposing pregnant IsoPreg dams to SocPreg bedding also accelerated homing onset in the offspring, though not to the same extent as the full social context. Thus, it appears that the facilitation of homing is mediated through the pregnant dam by a combination of chemical cues and other social stimuli.