The Salse di Nirano Regional Reserve is a special area of conservation situated in the lower slopes of the Modena Apennines, set up in 1982 to protect the largest and most particular group of mud volcanoes in Emilia Romagna.
Thanks to the presence of different natural and semi-natural habitats, which contain numerous species of animals needing protection, the Reserve has recently attracted the attention of a group of researchers from the Department of Life Sciences and Systems Biology of the University of Turin (DBIOS), specialized in the development of systems for Passive Acoustic Monitoring.
As part of the project, coordinated by Livio Favaro, carried out thanks to System’s contribution, the cooperation of the Municipality of Fiorano Modenese and the Ente di gestione per i parchi e la biodiversità Emilia Centrale (the Body responsible for managing parks and biodiversity in Central Emilia), acoustic recording stations were installed in strategic locations in the Reserve, composed of a hydrophone and a microphone.
Thanks to a latest-generation digital recorder connected to an integrated omnidirectional microphone and a hydrophone at a depth of 2 meters, 24/24 environmental recordings were acquired (10 minutes on – 20 minutes off) at a strategic point of the Salse di Nirano Reserve (Route n°7 – the “two lakes” area) identified by the UTM coordinates 44°50’71’’N; 10°82’02’’E n.
The recording system was activated for 365 days in the period between 09 February 2017 and 08 February 2018. Overall, 15,505 files in .wav format (sampling rate 48 kHz) were acquired for a total of over 155,000 hours of recordings for both the land and aquatic environments.
The recordings were then analyzed at the “c3s” interdepartmental research center of the University of Turin to calculate the following eco-acoustic indices: Acoustic Complexity Index, Acoustic Diversity Index, Acoustic Entropy Index and Normalized Difference Soundscape Index.
The results obtained over the full year of recordings have made it possible to develop a technologically advanced tool with no environmental impact for the study of the biological diversity of species of vertebrates present in the territory. In particular, spectrographic analysis of the recordings has permitted the researchers to obtain important information regarding the presence, abundance and behavior of the main species of birds, amphibians and mammals in the Reserve, studying them in their natural environment without disturbing or altering it.
In some cases, the bio-acoustic analysis has made it possible to recognize even the single individuals of a species present inside a certain territory and to compare their vocal behavior in relation to the environmental context, the different levels of human pressure, circadian rhythms and seasonality.
The creation of a sonic archive
A sub-sample of sounds containing the vocal sounds of the main species of songbirds present in the area of study has been identified, starting from original recordings stored in DBIOS. A number of sounds representative of the vocal repertoire of each species identified will be stored in Open Access form on the xeno-canto web archive (http://www.xeno-canto.org) after publication of the scientific results deriving from the bio-acoustic and eco-acoustic analyses. Each file will be associated with a unique identification code and the phrase “Acoustic recordings were collected within the Riserva Naturale delle Salse di Nirano (Fiorano M.se, Italy). Data collection was supported by the Department of Life Sciences and Systems Biology of the University of Torino through a System S.p.A. research grant”. In addition, each multimedia file will be protected under a Non-Commercial-NoDerivs License.
Passive Acoustic Monitoring is a new development compared to traditional methods, which involve long sessions in the field on the part of specialized operators, with consequent costs and use of human resources. As well as the innovate research results of national and international importance, the project has also allowed for a better understanding of the Modena territory and its biological diversity, a pool of knowledge that needs to be preserved and transmitted to future generations.