Temporal occurrence of three blue whale populations in New Zealand waters from passive acoustic monitoring

Temporal occurrence of three blue whale populations in New Zealand waters from passive acoustic monitoring Authors: Dawn R. Barlow1*, Holger Klinck2,3, Dimitri Ponirakis2, Mattea Holt Colberg1,4, Leigh G. Torres1 1Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA 2K. Lisa Yang Center for Conservation Bioacoustics, Cornell University, Ithaca, New York, USA 3Marine Mammal Institute, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Newport, Oregon, USA 4Department of Integrative Biology, Oregon State University, Corvallis, Oregon, USA *Correspondent: [e-mail] Abstract: Describing spatial and temporal occurrence patterns of wild animal populations is important for understanding their evolutionary trajectories, population connectivity, and ecological niche specialization, with relevance for effective management. Throughout the world, blue whales produce stereotyped songs that enable identification of separate acoustic populations. We harness continuous acoustic recordings from five hydrophones deployed in the South Taranaki Bight (STB) region of Aotearoa New Zealand from January 2016-February 2018. We examine hourly presence of songs from three different blue whale populations to investigate their contrasting ecological use of New Zealand waters. The New Zealand song was detected year-round with a seasonal cycle in intensity (peak February-July), demonstrating the importance of the region to the New Zealand population as both a foraging ground and potential breeding area. Antarctic song was present in two distinct peaks each year (June-July; September-October) and predominantly at the offshore recording locations, suggesting north and southbound migration between feeding and wintering grounds. Australian song was only detected during a 10-day period in January 2017, implying a rare vagrant occurrence. We therefore infer that the STB region is the primary niche of the New Zealand population, a migratory corridor for the Antarctic population, and outside the typical range of the Australian population.