Grace Smith-Vidaurre, Valeria Perez-Marrufo, Elizabeth A. Hobson, Alejandro Salinas-Melgoza, Timothy F. Wright

Animals can actively encode different types of identity information in communication signals, such as group membership, individual identity, or social status. The social environments in which animals interact may favor different types of information, but whether identity information conveyed in learned signals is resilient or responsive to short-term changes in the social environment is not well understood. We inferred the type of identity information that was most salient in vocal signals by combining computational tools, including supervised machine learning, with a conceptual framework of “hierarchical mapping”, or patterns of relative acoustic convergence across social scales. We used populations of an invasive vocal learning species as a natural experiment to test whether social environments altered over ecological timescales changed the type of identity information that different populations emphasized in learned vocalizations. We compared the social scales with the most salient identity information among native and invasive range monk parakeet (Myiopsitta monachus) calls recorded in Uruguay and the United States, respectively. We also evaluated whether the identity information emphasized in invasive range calls changed over time. To place our findings in an evolutionary context, we benchmarked our results with another parrot species that exhibits well-established and distinctive regional vocal dialects that are consistent with signaling group identity. We found that native and invasive range monk parakeet calls both displayed the strongest convergence at the individual scale and minimal convergence within sites. We did not identify changes in the strength of acoustic convergence within sites over time in the invasive range calls. These results indicate that the individual identity information in learned vocalizations was resilient to social environments perturbed over ecological timescales. Our findings point to exciting directions for further research on the responsiveness of communication systems to changes in the social environment over different evolutionary timescales.