North Atlantic right whale Eubalaena glacialis vocalization patterns in the central Gulf of Maine from October 2009 through October 2010

The central Gulf of Maine was recently identified as a persistent wintering ground and potential mating ground for non-calving North Atlantic right whales Eubalaena glacialis based on aerial survey data. However, these surveys were limited by bad weather and light. Here, we use passive acoustic monitoring to examine the long-term persistence of right whales in this area throughout a nearly continuous period from October 2009 through October 2010. Three archival marine acoustic recording units were deployed in the Outer Fall/central Gulf of Maine. The data were manually reviewed for right whale up-calls and gunshots to investigate seasonal and diel patterns. Up-calls and gunshots occurred seasonally, with the most calls recorded from October through January and fewer calls detected from February through July, increasing again in August through October. Up-calls were most frequent in November, and gunshots in December. There was a clear bimodal diel pattern in up-calls, with the majority of calls occurring between 04:00 through 08:00 h and 13:00 through 22:00 h. There was a clear peak in diel distribution of gunshots, with the majority of calls occurring between 16: 00 and 22:00 h. Our data demonstrate the continuous presence of right whales in the central Gulf of Maine during the winter months. The rate of gunshots during winter months in Outer Fall supports the hypothesis that male advertisement and/or right whale mating behavior may be taking place in this region at that time.