Passive acoustic monitoring is playing an increasing role in the detection of endangered North Atlantic right whales (NARW). Previous acoustic monitoring has relied on a single stereotyped vocalization, the upcall. Here the entire repertoire produced by NARW during the winter and early spring in Cape Cod Bay, Massachusetts is described. An objective sound classification scheme and automatic classification algorithm were developed. Nine days of acoustic recordings were used for the data analysis and a total of 9,611 right whale sounds were identified. The objective classification scheme of right whale sounds allowed for rapid identification of a diversity of right whale sounds. These sounds were assigned to 6 classes of narrowband upcalls, downsweep, complex and high frequency calls, wideband gunshot sounds and complex sounds. Results indicate that the prevalence of upcalls varied from 28% of detected calls in January to 80% in April. Other classes of signals were also well represented in the repertoire including the narrowband complex(10-36%) and high frequency calls (1-26%), wideband gunshot sounds (4-25%) and wideband complex sounds (0 – 25%). The prevalence of non-upcall signals suggests that including more signals classes may improve rates of detection for right whales in the Cape Cod Bay habitat.
Sound production behavior of individual North Atlantic right whales: implications for passive acoustic monitoring