Sons, cidades e sauins: efeitos do ambiente acústico no comportamento de comunicação do Sauim-de-Coleira (Saguinus bicolor)

Abstract

Sounds produced by animal species are often shaped by physical and acoustic environments in which they occur. Both biological and anthropogenic sounds can induce changes in acoustic signals of certain species. The pied tamarin (Saguinus bicolor) is a Critically Endangered primate with a narrow geographic distribution. To the north of its distribution, the pied tamarin interacts with the congeneric species red-handed tamarin (Saguinus midas). In contrast, the core of its distribution lies partly within the city of Manaus. This thesis investigated how the acoustic environment affects the communication behaviour of the pied tamarin. Analysis of the long calls (territorial sounds) of 15 groups of S. midas and S. bicolor reveled that the pied tamarin populations in sympatric areas did not show significant differences in vocalization compared to those that are in alloparty. On the other hand, sound character displacement was evident when comparing vocalizations of S. midas from sympatry and allopatry. The shifts involved had the effect of making the emitted sounds more similar to those of pied tamarins. The observed convergence can be attributed to the behaviour associated with the emission of the sound is, since similar sounds would be more effective in conveying information relating to between-species vocal territorial boundary marking in sympatric areas. Furthermore, the observed displacement occurred only in areas of primary, and not in secondary forests, which may be related to the difference in selective forces for sound propagation. This thesis also reports the effects of Manaus city noise on the communication behaviour of nine groups of pied tamarins. Pied tamarins did not increase or decrease the abundance of long calls in response to noise. However, the occurrence (1= occurred; 0= did not occur) of these vocalizations increased. It is possible that, when faced with intense noise, some of the group individuals emit a single long call to coordinate the group to move to quieter areas but not necessarily vocalise more often to do so. The abundance of emitted vocalisations was more influenced by social aspects, such as group size and distance from their territorial boundaries (a proxy for the interaction with neighbouring groups). In addition, there was no shift in the temporal pattern of vocalization emissions across the day in response to noise. However, at a finer scale, that of a long call, we found that the syllable repetition rate (number of syllables/duration) of long calls altered with calls being slower in noisier areas. As for the other acoustic parameters (duration, lower frequency, and frequency with higher energy), there were no significant relation with noise. Another strategy used probably to circumvent city noise is that pied tamarins scent mark more often in noisy environments. Despite this, they do not reduce their vocal behaviour; therefore, there is no evidence for multimodal communication shift, but probably complementation of the information contained in signals from different sensory channels. In summary, this shows that sounds of anthropic origin (noise), but not interaction with the red-handed tamarin, affect pied tamarin communication patterns.