Olfactory, thermal, and tactual influences on infantile ultrasonic vocalization in rats

The amount of time infant rats 3–13 days old spent emitting ultrasounds was greater when pups were placed in an empty dish than when placed in a dish containing clean bedding or soiled bedding from the nest. Pups from 5–13 days of age vocalized more when on the clean bedding than when on the soiled bedding. When placed on cloth covered dishes, pups vocalized most to the empty dish and least to the dish containing soiled bedding. The odor of clean bedding elicited less ultrasonic vocalization than the odor of the empty dish only when pups were less than 7 days old. Pups vocalized more to room temperature than to heated conditions. The results indicate that olfactory, tactual, and thermal nest cues influence infantile ultrasonic vocalization in the rat.