Female perception of size-related formant shifts in red deer, Cervus elaphus

Little is known about the role of specific acoustic cues in mammal vocal communication systems. In the current study, we used resynthesized male red deer roars in a habituation–discrimination paradigm to determine whether female red deer are sensitive to shifts in formant frequencies corresponding to the natural variation between the vocal tract lengths of a small and large adult red deer male. Hinds habituated to a given size variant showed a significant dishabituation when they were presented with roars in which the formants had been modified to simulate the other size variant. The significant reduction in behavioural response to a final rehabituation playback showed this was not a chance rebound in response levels. Our results suggest that formants are salient for red deer hinds and that hinds can detect a shift in formant frequencies that may have biological significance. We discuss the possible functions of formant perception in female red deer and more generally in nonhuman mammals.