Print PageVertebrates produce various auditory, olfactory, tactile, and visual signals that function to attract mates, deter rivals, warn conspecifics of predators or alert offspring to the presence of parents with food. Alarm signals, such as vocalizations, play a critical role in the social structure of group-living mammals and have been the focus of considerable field research. In some mammals, the characteristics of a signal vary across geographical ranges and can be population-specific. An important question to ask is ‘what are the environmental and genetic sources of intraspecific variation in auditory signals?’ The ability to manipulate vocal signal integrity is limited by anatomical features such as body size, ear structure and other phylogenetic constraints, but could be equally influenced by the environmental variables. I conducted a two population study in 2010 on the trilling alarm call vocalization of Spalacopus cyanus, a social subterranean rodent endemic to central Chile. Ecological data and acoustic recordings were collected to determine the relative importance of intraspecific variation in ecology, genetics, and body size on S. cyanus alarm calls. Data was collected from 22 individual S. cyanus from Fundo Rinconada de Maipú and 50 individuals from La Parva, Chile. Recordings were made upon capture for up to 10 minutes if alarm calls were produced. Measurements were taken on body weight and size. A phylogentic study on S. cyanus was published in 2009 to correlate data. Sound analysis software was used to analyze vocalizations.
Results/Conclusions
Preliminary observations from 2009 in Fundo Rinconada de Maipú and Fray Jorge National Park suggest alarm calls may vary considerably across the geographical range of the species. A preliminary laboratory investigation on comparing vocalizations from a mountain population, La Parva, and a coastal population, Los Molles, demonstrated differences in syllable structure. There was a difference in average high frequency of nearly 2250 Hz between the two populations. The peak power was 10 dB lower on average from the mountain S. cyanus. Ecological data in conjunction with analysis of calls using spectrogram software will provide insight into factors most greatly influencing alarm call maintenance and variation among populations. Research linking sources of variation influencing alarm calls can improve our understanding of proximate and ultimate causation. Determining these and other sources of geographical variation in animal vocalizations contributes to a greater understanding of the evolution of communication systems.
