Comparison of vocalisations of introduced European red deer stags (Cervus elaphus) in north-western Patagonia (Argentina) with native European populations

Abstract

Polygynous deer are very vocal species, producing calls in various contexts. Male rutting calls in red deer (Cervus elaphus) have been most studied in captive and/or free-ranging European populations. The recent application of ‘source-filter theory’ has identified the independent roles of fundamental frequency (F0) and formants in the production of deer calls and demonstrated the relation between formant spacing and anatomical characteristics such as body size. The present paper describes and characterises the acoustical properties of male rutting vocalisations for a free-ranging red deer population located in the ecotone of the eastern Andean cordillera within the Nahuel Huapi National Reserve (Neuquén, Argentina), and is the first acoustic study of free-ranging red deer stags outside their historic distribution. Recordings were made of seven identified and several unidentified stags at the peak of the rut in 2007. Calculated F0 was found to be higher for these identified stags than for Scottish red deer on the island of Rhum. The analysis of formant spacing was used to calculate the length of the vocal tract (VTL) for the seven males studied; values were comparable to those found in stags from Rhum. The longest calculated VTLs within these males corresponded to those of the four stags with the largest antler racks and the only stags holding harems. Previous studies have shown that VTL correlates with body size, age and reproductive success and that these deer have the ability to lower their larynx and extend their vocal tracts to a maximum, which is probably under sexual selection. Our data fit with this explanation. The higher F0s recorded in this population may result from the influence of wapiti genes, known to be present in these deer, because wapiti have a much higher-frequency rutting call, namely, the bugle. Alternatively, they may be related to the mating strategy, which differs substantially from the northern European populations.