Maturation of the vocal production system cannot solely explain the acquisition of the adult trill call in infant grey mouse lemurs

During vocal ontogeny grey mouse lemurs gradually acquire their adult trill call. It is not clear whether this is a result of maturation or vocal learning. To test for the impact of maturation, we investigated whether age-dependent changes of acoustic parameters can be explained by infant growing and to which extent individual signatures are shaped by genetic relatedness.

We measured the tempo-spectral acoustic parameters of 1855 syllables of 266 infant calling bouts (N=14 families) recorded during four infant developmental stages and 50 adult trills (N=38). Conducting unsupervised cluster analysis, we defined syllable types and compared their occurrence for the first, middle and end part of the bouts across age classes. To investigate the impact of genetics on individual signatures, we performed a discriminant function analysis and compared acoustic and genetic similarity using a data set of 431 adult trills (N=30 individuals).

Inconsistent patterns for age-dependent changes on the tempo-spectral parameters for syllable position and syllable types were found, which could not be solely explained by maturation of the vocal production system. A higher variation in syllable types and temporal parameters was shown for the first syllable compared to the middle or end part of the calling bouts showing its potential in encoding individual identity. This was supported by the first syllable showing a higher degree of individual distinctiveness than the middle and end syllables. Preliminary analysis showed no correlation between acoustic and genetic similarity. Thus, ongoing analyses will investigate the impact of social partners on trill call structure.