Neonatal ultrasounds elicited by odor cues.

Ultrasounds were monitored from neonatal rats following placement on 1 of 5 types of bedding material. Odors associated with the home cage or an adult male inhibited neonatal ultrasonic signaling. Odors associated with a novel lactating female elicited initially high rates of signaling, the rate lowering across the age range of pups tested. Odors associated with a novel virgin female or with an absence of animal odors elicited increasing rates of signaling across the age range tested.