Decadal‐scale phenology and seasonal climate drivers of migratory baleen whales in a rapidly warming marine ecosystem

• Published in: Global change biology 2022-08, Vol.28 (16), p.4989-5005
• Main Authors: Pendleton, Daniel E., Tingley, Morgan W., Ganley, Laura C., Friedland, Kevin D., Mayo, Charles, Brown, Moira W., McKenna, Brigid E., Jordaan, Adrian, Staudinger, Michelle D.
• Format: Article
• Language: English
• Subjects: Animal Migration - physiology; Animals; Aquatic mammals; Balaenoptera physalus; Baleens; Cetacea; Climate change; Ecosystem; endangered species; Eubalaena glacialis; Evaluation; Feeders; fin whale; Fins; Gulf of Maine; Habitat selection; Habitat utilization; Habitats; Hot springs; Human-wildlife relations; humpback whale; Marine ecosystems; Marine mammals; Megaptera novaeangliae; North Atlantic right whale; ocean warming; Oceans and Seas; Phenology; Protected species; Seasons; Spring; Spring (season); Whales; Whales & whaling; Whales - physiology; Wildlife; Wildlife habitats; Wildlife management
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.16225

Species' response to rapid climate change can be measured through shifts in timing of recurring biological events, known as phenology. The Gulf of Maine is one of the most rapidly warming regions of the ocean, and thus an ideal system to study phenological and biological responses to climate change. A better understanding of climate‐induced changes in phenology is needed to effectively and adaptively manage human‐wildlife conflicts. Using data from a 20+ year marine mammal observation program, we tested the hypothesis that the phenology of large whale habitat use in Cape Cod Bay has changed and is related to regional‐scale shifts in the thermal onset of spring. We used a multi‐season occupancy model to measure phenological shifts and evaluate trends in the date of peak habitat use for North Atlantic right (Eubalaena glacialis), humpback (Megaptera novaeangliae), and fin (Balaenoptera physalus) whales. The date of peak habitat use shifted by +18.1 days (0.90 days/year) for right whales and +19.1 days (0.96 days/year) for humpback whales. We then evaluated interannual variability in peak habitat use relative to thermal spring transition dates (STD), and hypothesized that right whales, as planktivorous specialist feeders, would exhibit a stronger response to thermal phenology than fin and humpback whales, which are more generalist piscivorous feeders. There was a significant negative effect of western region STD on right whale habitat use, and a significant positive effect of eastern region STD on fin whale habitat use indicating differential responses to spatial seasonal conditions. Protections for threatened and endangered whales have been designed to align with expected phenology of habitat use. Our results show that whales are becoming mismatched with static seasonal management measures through shifts in their timing of habitat use, and they suggest that effective management strategies may need to alter protections as species adapt to climate change. In examining potential impacts of climate change, we found significant shifts in peak habitat use dates for large whales, including endangered North Atlantic right whales, of almost three weeks over 21 years. Earlier spring onset resulting from rapid ocean warming in the Gulf of Maine was related to shifts in the timing of peak whale habitat use. We found significantly increased right whale habitat use during spring, when fishing and shipping restrictions are typically relaxed. Changing seasonality of whale o