Vocal anatomy, tongue protrusion behaviour and the acoustics of rutting roars in free-ranging Iberian red deer stags (Cervus elaphus hispanicus) Roland Frey, 1 Ilya Volodin, 2,3 Elena Volodina, 3 Juan Carranza 4 and Jero ´ nimo Torres-Porras 4 1 Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin, Germany 2 Department of Vertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia 3 Scientific Research Department, Moscow Zoo, Moscow, Russia 4 Ungulate Research Unit, CRCP, Co ´ rdoba University, Campus de Rabanales, Co ´ rdoba, Spain Abstract Roaring in rutting Iberian red deer stags Cervus elaphus hispanicus is unusual compared to other subspecies of red deer, which radiated from the Iberian refugium after the last glacial maximum. In all red deer stags, the larynx occupies a permanent low mid-neck resting position and is momentarily retracted almost down to the rostral end of the sternum during the production of rutting calls. Simultaneous with the retraction of the larynx, male Iberian red deer pronouncedly protrude the tongue during most of their rutting roars. This poses a mechanical challenge for the vocal tract (vt) and for the hyoid apparatus, as tongue and larynx are strongly pulled in opposite directions. This study (i) examines the vocal anatomy and the acoustics of the rutting roars in free-ranging male C. e. hispanicus; (ii) establishes a potential mechanism of simultaneous tongue protrusion and larynx retraction by applying a two-dimensional model based on graphic reconstructions in single video frames of unrestrained animals; and (iii) advances a hypothesis of evaporative cooling by tongue protrusion in the males of a subspecies of red deer constrained to perform all of the exhausting rutting activities, including acoustic display, in a hot and arid season. Key words: Cervidae; evaporative cooling; larynx retraction; respiratory tract; ruminants; rutting roars; sexual selection; thermoregulation; vocalization. Introduction Rutting red deer stags (Cervus elaphus) use vocal displays both for deterring rival males and for attracting receptive females (Reby et al. 2005; Charlton et al. 2007a). Patterns of rutting roars differ markedly between subspecies (Tembrock, 1965; Nikol’skii et al. 1979; Reby & McComb, 2003a; Feighny et al. 2006; Kidjo et al. 2008). This vocal diver- gence may result from different phylogeographic origins of the respective subspecies (Ludt et al. 2004; Zachos & Hartl, 2011), from different vocal morphologies (Riede et al. 2010), from sexual selection by female preferences for certain roar acoustics (Charlton et al. 2007a; Reby et al. 2010), or from environmental factors acting on the stags during the rut. During the last Pleistocene glacial maximum, red deer dis- tribution in Europe was restricted to four isolated sites: the Iberian Peninsula ⁄ Southern France, Italy, the Balkans and the Carpathians (Zachos & Hartl, 2011). The Iberian C. e. hi- spanicus, Scottish C. e. scoticus, and Norwegian C. e. ela- phus subspecies originate from the same Iberian ⁄ Southern France refuge and share the same mitochondrial cyto- chrome b A-haplotype group. In contrast, the B-haplotype group of Corsican red deer C. e. corsicanus and C. e. barba- rus suggests a distinctive origin of these subspecies (Skog et al. 2009; Niedzialkowska et al. 2011; Zachos & Hartl, 2011). Red deer re-colonization in Europe after the last Ice Age was influenced by ecological factors: climate, landscape, food availability and habitat acoustics. These factors accounted for the divergence in fur cover, body size, behav- iour and acoustic communication between subspecies. In Spanish red deer stags the neck mane is lacking, whereas in red deer inhabiting the colder parts of Europe, the neck region is accented by a heavy mane (Wagenknecht, 1983; Fitch & Reby, 2001), suggesting some sort of thermoregula- tory function, in addition to the ‘strong neck performance’ that is applied during the rut to pretend to have larger neck muscles, i.e. better fighting ability, by ruffling up the neck Correspondence Roland Frey, Leibniz Institute for Zoo and Wildlife Research (IZW) PO Box 60 11 03, D-10252 Berlin, Germany. E: frey@izw-berlin.de Accepted for publication 5 December 2011 Article published online 19 January 2012 ª 2012 The Authors Journal of Anatomy ª 2012 Anatomical Society J. Anat. (2012) 220, pp271–292 doi: 10.1111/j.1469-7580.2011.01467.x Journal of Anatomy