Whale Acoustic Ecologies and Habitats: Insights from Marine Acoustic Networks

Long-term, large-scale data from acoustic monitoring networks operating in different ocean areas frequented by whales reveal acoustic features of those habitats. These moored seafloor systems continuously sample the acoustic environment, and resultant data provide a means for mapping, quantifying and describing the spatio-spectral-temporal variability of a whale’s acoustic habitat over ecologically meaningful scales. By focusing on the 1/3^rd octave frequency bands used by different species for long-range communication, we measured the acoustic dynamics of their primary communication channels. We present a model, richly informed by empirical data, to quantify the effect of masking on whale acoustic communication. Acoustic data were from long-term acoustic monitoring systems sampling the low-frequency range (< 1000Hz) throughout whale habitat for periods of months to years. Resultant acoustic data were analyzed to map, quantify and describe the spatio-spectral-temporal variability of the acoustic habitat over ecologically meaningful scales. Ship GIS movements and source characteristics were documented from the US Coast Guard’s Automatic Information System and acoustic recorders, respectively. Results reveal the extent to which different sources of sound in the ocean, both natural and man-made, influence the probability of long-range communication. In waters off New England with high rates of vessel traffic and high levels of vessel noise, the predicted areas over which whales can communicate are now reduced to a small proportion (< 20 - 80%) of what they would be under quiet conditions. When considered from a large-scale and behavioral ecological perspective, this reduction in acoustic communication habitat, as measured in terms of the proportional loss of an individual’s or population’s communication space, likely represents a significant loss and cost for endangered species such as the right whale, in which acoustic communication is known to serve critical biological functions.