Acoustic codes from a rural sanctuary: How ecoacoustic events operate across a landscape scale

Abstract

Sonotopes are the acoustic patches of a soundscape, composed by different occurrences of geophonies, biophonies, and technophonies. According an ecosemiotic perspective, ecoacoustic events (EEs) are the vehicles from the attribution of meaning to the emergent sonotopes and work as neural codes. The process of encoding is suggested to be active between the perception of sonotopes and EE detection. In Ortolano Rural Sanctuary, from a grid of 12 acoustic digital recorders (ADRs) at an average distance of 30 m each with a microphone set to receive sounds from a near acoustic field, 824,160 one-minute acoustic files were obtained from October 2017 to September 2018. From these files, using the combination of three acoustic complexity indices (ACIft, ACIft evenness, and ACItf evenness), through the ecoacoustic event detection and identification (EEDI) procedure, more than 200 EEs on average per ADR were extracted during this period. The EEs were seasonally aggregated with a significant separation between fall-winter and spring-summer periods. Rain and wind were important in EE composition according to location and seasonality. The number of EEs detected from just one month to three months was 57% of the total, and the first of the nine classes of ACIft belonged to 78% of all classes of abundance. The EEs and ACItf similarity were not correlated with the distance between ADRs, confirming the correctness of the near-field approach to detect sounds from landscapes and EE spatial independence. The ranging capacities to distinguish distance from sound sources and to discriminate the temporal and frequential patterns of acoustic signals are some of the mechanisms that species use to detect and encode environmental acoustic complexity. Species are supposed to use EE to explore and assess the acoustic habitat and probably to obtain mental maps of the surroundings they must move around using an acoustic exploration.