Geographic variation in loud calls of sportive lemurs (Lepilemur ssp.) and their implications for conservation.

Bioacoustical studies in nonhuman primates have shown that loud calls can be reliably used as a noninvasive diagnostic tool for discriminating cryptic taxa, for their monitoring in the field as well as for the reconstruction of their phylogeny. To date, it is unknown, whether loud calls can be used for these purposes in sportive lemurs, for which current genetic studies suggest the existence of at least 24 cryptic species. The aim of this study was to compare the structure of loud calls of populations of sportive lemurs to characterize informative acoustic traits for taxa discrimination and to establish a phylogenetic tree based on acoustic structure. We have based our study on Inter-River-Systems (IRSs) as operational taxonomic units. Samples were collected from nine different localities of four IRSs along a transect from northwestern to northern Madagascar. Two call types, the ouah and the high-pitched call, were present in almost all IRSs. Six temporal and eight spectral parameters were measured in 196 calls of the best quality given by 21 different males. Variation within and between IRSs was assessed by multivariate statistics. Loud calls differed significantly among the different IRSs. The IRSs varied most in spectral parameters, whereas temporal parameters were less variable. Phylogenetic analysis using parsimony yielded 11 out of 17 acoustic characters as phylogenetically informative. The acoustic tree had an average branch support of 78%. Its topology coincided less with geographic distances than with genetic tree topology. Altogether our findings revealed that loud calls separated geographically isolated populations of sportive lemurs specifically. Based on these results, noninvasive tools for diagnosis and monitoring of cryptic species in nature can be developed for conservation management.