Is there an acoustic difference between the contact calls of the coati (Carnivora: Procyonidae: Nasua nasua Linnaeus, 1766) in the south of its distribution?

Abstract

Coatis (Nasua nasua) form extensive social groups and utilize acoustic signals as one of their means of communication. The contact call, chirp, plays an important role in maintaining cohesion and exchanging information. Our objective was to evaluate possible regional differences in chirp parameters in the Atlantic Forest and Pampa biomes from southern Brazil and Uruguay, and investigate the relationship between environmental variables and this signal, testing the Acoustic Adaptation Hypothesis (AAH). We obtained audios from 184 videos of camera traps distributed in the two biomes. Temporal and spectral parameters were extracted from the chirps and organized with the respective environmental variables and location. We found significant differences for all chirps’ parameters at biome and locality levels. The environmental predictors most consistently associated with vocal variation were NDVI, latitude and wind speed, although NDVI and latitude likely reflect the same environmental gradient. Animals in environments with dense vegetation tend to vocalize at lower frequencies, probably due to attenuation generated by vegetation, whereas calls emitted in open environments tended to exhibit higher frequencies, consistent with the predictions of the AAH. These findings are consistent with the Acoustic Adaptation Hypothesis and suggest that environmental conditions may contribute to acoustic variation in coati contact calls.