Acoustic divergence in the rut vocalizations of Persian and European fallow deer

We conducted a study of the male rut vocalizations (groans) of two closely related species, Persian and European fallow deer. Persian fallow deer are endangered, restricted to Iran and Israel, and their rut vocalizations have never been studied. By contrast, European fallow deer are one of the most common deer species in the world, and have been the subject of numerous detailed studies. Persian bucks are approximately 16% larger than European bucks, and this can have important implications for vocalizations. Persian bucks were recorded in Israel, and European bucks were recorded in the UK and Ireland. We measured temporal, fundamental frequency-related and formant-related parameters of groans and determined which acoustic parameters differed among species and populations. The comparisons revealed important structural similarities and differences, with the differences more strongly related to temporal than spectral vocal parameters. Persian buck groans were relatively long, pulsed calls of almost 1-s duration, with low fundamental frequencies, and relatively weak formant modulation. European buck groans were much shorter (0.38s), but with similarly low fundamental frequencies and clearer formant modulation. We found some minor differences in the formant frequencies (F4 and F5) of calls of the two European fallow populations. Given the length of time since Persian and European fallow deer diverged, and that both their mitochondrial and nuclear genomes are very different, it is notable that the structure of their groans is still so similar. Our findings suggest that the factors influencing the evolution of these vocalizations (e.g. sensory system characteristics, environment and mate choice) have probably been similar for both species.