Cross fostering experiments suggest that mice songs are innate

Background

Vocal learning is a central functional constituent of human speech, andrecent studies showing that adult male mice emit ultrasonic sound sequencescharacterized as “songs” have suggested that the ultrasoniccourtship sounds of mice provide a mammalian model of vocal learning.

Objectives

We tested whether mouse songs are learned, by examining the relative role ofrearing environment in a cross-fostering experiment.

Methods and Findings

We found that C57BL/6 and BALB/c males emit a clearly different pattern ofsongs with different frequency and syllable compositions; C57BL/6 malesshowed a higher peak frequency of syllables, shorter intervals betweensyllables, and more upward frequency modulations with jumps, whereas BALB/cmales produced more “chevron” and “harmonics”syllables. To establish the degree of environmental influences in mouse songdevelopment, sons of these two strains were cross-fostered to another strainof parents. Songs were recorded when these cross-fostered pups were fullydeveloped and their songs were compared with those of male mice reared bythe genetic parents. The cross-fostered animals sang songs with acousticcharacteristics - including syllable interval, peak frequency, andmodulation patterns - similar to those of their genetic parents. In additiontheir song elements retained sequential characteristics similar to those oftheir genetic parents'' songs.

Conclusion

These results do not support the hypothesis that mouse “song” islearned; we found no evidence for vocal learning of any sort under theconditions of this experiment. Our observation that the strain-specificcharacter of the song profile persisted even after changing thedevelopmental auditory environment suggests that the structure of thesecourtship sound sequences is under strong genetic control. Thus, theusefulness of mouse “song” as a model of mammalian vocallearning is limited, but mouse song has the potential to be an indispensablemodel to study genetic mechanisms for vocal patterning and behavioralsequences.