The impact of the “Anthropause” on the communication and acoustic habitat of Southeast Alaskan humpback whales

The COVID-19 pandemic caused profound changes in global human behavior, including substantial decreases in marine transportation, a pervasive ocean noise source. The human tragedy of the pandemic provides an unprecedented opportunity to investigate how humpback whales communicate in the absence of chronic noise common to their acoustic habitats. The Alaskan tourism industry was impacted particularly strongly; Southeast Alaska experienced a near complete absence cruise ships during the 2020 tourism season (May—September). In summer 2019 and 2020, we deployed a SoundTrap hydrophone in Glacier Bay National Park to document vessel-generated ambient noise and vocal characteristics of humpback whales (Megaptera novaeangliae) which have been studied in this region since the 1980’s. In the absence of cruise ships, underwater noise from vessels was significantly lower in Glacier Bay compared to 2019. Median daily noise levels (dB_RMS 100–1500 Hz) were three times quieter during 2020 than in 2019. Preliminary analyses of humpback whale calling behavior show an increased number of call types in 2020 compared to the same period in 2019. Documenting humpback whale communication in quiet conditions can help illuminate impacts of chronic vessel noise and aid the development of measures to reduce human impacts in this and other marine protected areas.