Abstract
The evaluation of acoustic temporal rhythms in wide-ranging cetaceans can reveal patterns in animal spatial presence and the occurrence of periodical phenomena. Here, we aimed at assessing the temporal patterns of dolphin’s acoustic presence in a shallow-water area in the Sicily Strait (Mediterranean Sea). Whistles were collected continuously for 14 months from an acoustic monitoring station installed aboard of an elastic seamark. Over a total of 6955 h of recording, 14,048 signals were identified using both automatic and visual methods. Three parameters were analyzed: hourly presence (HP), used as a proxy of the presence of dolphins in the area; detection rate (DR), indicating the acoustic activity rate of dolphins measured per hour in the entire dataset; and detection rate in presence of dolphins (DRD), indicating the acoustic activity rate of dolphins considering only the hours when whistles were recorded. The highest values of both HP and DR were reached during the night, and the Autumn and Winter months, suggesting an increase in the dolphin’s occurrence and a possible moving away and towards the monitoring station potentially following prey. DRD, instead, showed an almost uniform distribution throughout the day implying that when the animals are close to the monitoring station, the acoustic activity does not show any pattern. However, possible changes in the communication exchange along the seasons were suggested. This study complements other work on this subject, improving the knowledge of dolphins’ acoustic activity in the area.
Highlights
Environmental cycles such as seasonal changes, light and dark alternation, lunar phases and tidal cyclicity influence biological rhythms and may have either independent or cumulative effects on activity timing of living organisms [1]
Acoustics is critical for the survival of several living organisms, which rely on sounds for carrying on biological activities and communicating
4.249 signifi0.116 ferences in Summer compared to Winter and Autumn months, while detection rate in presence of dolphins (DRD)
Summary
Environmental cycles such as seasonal changes, light and dark alternation, lunar phases and tidal cyclicity influence biological rhythms and may have either independent or cumulative effects on activity timing of living organisms [1]. Living organisms often evolve their physiological, biological, and behavioral activity to match with key cycles affecting their habitat [2]. Acoustics is critical for the survival of several living organisms, which rely on sounds for carrying on biological activities and communicating. Temporal and spatial patterns in the acoustic behavior of living organisms can reveal several phenomena. Reproductive and mating behaviors are one of the ultimate causes of periodicity in acoustic activity, and substantial variations can occur along seasons and daytime [5,7,8,9,10,11]
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