6 research outputs found
Ecoacoustics and multispecies semiosis: naming, semantics, semiotic characteristics, and competencies
Biosemiotics to date has focused on the exchange of signals between organisms, in line with bioacoustics; consideration of the wider acoustic environment as a semiotic medium is under-developed. The nascent discipline of ecoacoustics, that investigates the role of environmental sound in ecological processes and dynamics, fills this gap. In this paper we introduce key ecoacoustic terminology and concepts in order to highlight the value of ecoacoustics as a discipline in which to conceptualise and study intra- and interspecies semiosis. We stress the inherently subjective nature of all sensory scapes (vivo-, land-, vibro- and soundscapes) and propose that they should always bear an organismic attribution. Key terms to describe the sources (geophony, biophony, anthropophony, technophony) and scales (sonotopes, soundtopes, sonotones) of soundscapes are described. We introduce epithets for soundscapes to point to the degree to which the global environment is implicated in semiosis (latent, sensed and interpreted soundscapes); terms for describing key ecological structures and processes (acoustic community, acoustic habitat, ecoacoustic events) and examples of ecoacoustic events (choruses and noise) are described. The acoustic eco-field is recognized as the semiotic model that enables soniferous species to intercept core resources like food, safety and roosting places. We note that whilst ecoacoustics to date has focused on the critical task of the development of metrics for application in conservation and biodiversity assessment, these can be enriched by advancing conceptual and theoretical foundations. Finally, the mutual value of integrating ecoacoustic and biosemiotics perspectives is considered
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Gray whale migration patterns through the Southern California Bight from multi-year visual and acoustic monitoring
Sightings and acoustic recordings from eastern North Pacific gray whales in the Southern California Bight were analyzed for interannual changes and compared with concurrent environmental measurements during 7 migration seasons (2008−2009 to 2014−2015). Acoustic call counts recorded on an offshore hydrophone were highly variable from year to year. Assuming an average calling rate of 7.5 calls whale–1 d–1, the estimated number of whales migrating by this hydrophone would be <10% of the population within 20 km of the offshore hydrophone in most years. In contrast, the estimated number of gray whales migrating off Santa Barbara and Los Angeles based on visual surveys grew at a greater rate (11% yr−1 and 26% yr−1, respectively) than the population size growth rate (5% yr−1). Over the studied migration seasons it seems an increasing proportion of the population was using the nearshore migration corridor in the Southern California Bight, especially near Los Angeles. This trend could increase the negative anthropogenic impact on this species. Although several large-scale climatic events occurred between 2008 and 2015, neither water temperature in the Southern California Bight nor sea ice timing in the gray whale Arctic feeding area improved generalized additive models of gray whale nearshore sightings or offshore acoustic presence. Over these times, the gray whale migration timing appears to be driven more by their biological clock and instinct than by the extrinsic factors accounted for in the present analysis. Future work should test if other factors influence the gray whale migration over longer timescales