Upcalling behaviour and patterns in North Atlantic right whales, implications for monitoring protocols during wind energy development

Offshore wind energy is rapidly developing in US waters, with construction underway off Southern New England (SNE), an important region for many species, including the critically endangered North Atlantic right whale (NARW). A data-driven understanding of NARW upcalling behaviour is presented here to help establish proper monitoring protocols for mitigating impacts. Analyses of individual upcalls from 2 years of acoustic recordings showed that NARWs were detected at least 1 day every week throughout both years, with highest NARW presence from October to April. Weeks with more days of acoustic presence typically had more hours with calling activity, but the number of upcalls within a day or hour was variable, reflective of the social function of the upcall. Within SNE, on average, 95% of the time NARWs persisted for 10 days, and reoccurred again within 11 days. An evaluation of the time period over which it is most effective to monitor prior to commencing pile driving activities showed that with 1 h of pre-construction monitoring there was only 4% likelihood of hearing a NARW, compared to 74% at 18 h. Therefore, monitoring for at least 24 h prior to activity will increase the likelihood of detecting an up-calling NARW.