21The diversity of qualitative approaches and analytical methods has often undermined 22 comparative research on primate vocal repertoires. The purpose of the present work is 23 to introduce a quantitative method based on dynamic time warping to the study of 24 repertoire size in Eulemur spp. We obtained a large sample of calls of E. coronatus, 25
E. flavifrons, E. fulvus, E. macaco, E. mongoz, E. rubriventer and E. rufus, recorded 26between 1999 and 2013 from captive and wild lemurs. We inspected recordings 27 visually using spectrograms, then cut and saved high-quality vocal emissions to single 28 files for further analysis. We extracted the acoustic features of all vocalizations of a 29 species using the Hidden Markov Model toolkit, an application of dynamic time 30warping, then compared cepstral coefficients (a feature widely used in automatic 31 speaker recognition) pairwise. We analysed the results using Affinity Propagation 32 clustering. We found that Eulemur species share most of their vocal repertoire but 33 species-specific calls determine repertoire size differences. Repertoire size varied 34 from 9 and 14 vocalisation types among species, with a mean of 11. Group size is 35 thought to favour the evolution of vocal complexity at the species level but our results 36 suggest that this relationship should be reconsidered, as Eulemur rubriventer has the 37 largest vocal repertoire but shows a relatively small average group size when 38 compared to congeneric species.
Soundscapes have been likened to acoustic landscapes, encompassing all the acoustic features of an area. The sounds that make up a soundscape can be grouped according to their source into biophony (sounds from animals), geophony (sounds from atmospheric and geophysical events), and anthropophony (sounds from human activities). Natural soundscapes have changed over time because of human activities that generate sound, alter land-use patterns, remove animals from natural settings, and result in climate change. These human activities have direct and indirect effects on animal distribution patterns and (acoustic) behavior. Consequently, current soundscapes may be very different from those a few hundred years ago. This is of concern as natural soundscapes have ecological value. Losing natural soundscapes may, therefore, result in a loss of biodiversity and ecosystem functioning. The study of soundscapes can identify ecosystems undergoing change and potentially document causes (such as noise from human activities). Methods for studying soundscapes range from listening and creating visual (spectrographic) displays to the computation of acoustic indices and advanced statistical modeling. Passive acoustic recording has become an ecological tool for research, monitoring, and ultimately conservation management. This chapter introduces terrestrial and aquatic soundscapes, soundscape analysis tools, and soundscape management.
The decline of the mongoose lemur Eulemur mongoz has resulted in a change of its conservation status from Vulnerable to Critically Endangered. Assessing the current threats to the species and the attitudes of the people coexisting with it is fundamental to understanding whether and how human impacts may affect populations. A questionnaire-based analysis was used to study the impact of agriculture and other subsistence activities, and local educational initiatives, on lemur abundance, group size and composition in the Comoros. On the islands of Mohéli and Anjouan we recorded lemurs in groups, the size and composition of which depended both on environmental parameters and the magnitude and type of anthropogenic pressure. There was no evidence of an impact of anthropogenic disturbance on abundance. In contrast, group size and composition were sensitive to human impacts. The most important threats were conflicts related to crop raiding, as well as illegal capture and hunting. The promotion of educational activities reduced the negative impact of hunting and illegal activities. These results highlight a need for urgent conservation measures to protect the species.
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