Phenotype constrains the vocal tract in the most dimorphic mammal, the southern elephant seal (Mirounga leonina).

The article discusses research which estimated the vocal tract length of wild male southern elephant seal during their normal vocalization behavior, using two dimensional (2D) videogrammetry. Topics covered include the feasibility of noninvasive vocal tract measurement in wild male southern elephant seals, the repeatability of several vocal tract measures and the correlation between them, and the association between the vocal tract and the structural phenotype that may constrain it.