Abstract
We provide a detailed description of the rutting vocalisations of free-ranging male Iberian deer (Cervus elaphus hispanicus, Hilzheimer 1909), a geographically isolated and morphologically differentiated subspecies of red deer Cervus elaphus. We combine spectrographic examinations, spectral analyses and automated classifications to identify different call types, and compare the composition of the vocal repertoire with that of other red deer subspecies.Iberian stags give bouts of roars (and more rarely, short series of barks) that are typically composed of two different types of calls. Long Common Roars are mostly given at the beginning or at the end of the bout, and are characterised by a high fundamental frequency (F0) resulting in poorly defined formant frequencies but a relatively high amplitude. In contrast, Short Common Roars are typically given in the middle or at the end of the bout, and are characterised by a lower F0 resulting in relatively well defined vocal tract resonances, but low amplitude. While we did not identify entirely Harsh Roars (as described in the Scottish red deer subspecies (Cervus elaphus scoticus)), a small percentage of Long Common Roars contained segments of deterministic chaos.We suggest that the evolution of two clearly distinct types of Common Roars may reflect divergent selection pressures favouring either vocal efficiency in high pitched roars or the communication of body size in low-pitched, high spectral density roars highlighting vocal tract resonances. The clear divergence of the Iberian red deer vocal repertoire from those of other documented European red deer populations reinforces the status of this geographical variant as a distinct subspecies.
Highlights
Vertebrate vocal signals are characterised by a very strong acoustic diversity: vocalisations can differ considerably between closely related species [1] and, within species, between subspecies [2,3] or even between geographically isolated populations [4,5,6]
The calls contained in the 1st group, identified as Long Common Roars (LCR) were roars characterised by a long duration (1.8360.12 s), a high max F0 (207.269.0 Hz), and the absence of Deterministic Chaos (DC)
The calls contained in the 2nd group were identified as Long Common Roars with deterministic chaos (LCRDC), and were characterised by the presence of segments of DC as well as a long duration (2.1160.14s) and a high max F0 (220.3610.8 Hz)
Summary
Vertebrate vocal signals are characterised by a very strong acoustic diversity: vocalisations can differ considerably between closely related species [1] and, within species, between subspecies [2,3] or even between geographically isolated populations [4,5,6]. Very closely related populations evolving in different habitats can evolve vocalizations which serve the same overall function but which make very different use of the acoustic space [13,17]. Selection pressures have favoured the evolution of species-specific signals with acoustic properties that either optimise their active space [24], facilitate localization accuracy [25] in the species’ habitat or reliably encode information about the individual’s physical quality and social status [26,27,28,29]
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