Behavior and inter-island movements of satellite-tagged humpback whales in Hawai’i, USA

Abstract

Humpback whales Megaptera novaeangliae encountered off the island of Kaua’i, Hawai’i, USA, in 2017, 2018, and 2019 were photo-identified, and 19 whales were equipped with satellite telemetry tags to track their inter-island movements and use their movement behavior to estimate when and where the whales changed their behavior from breeding to migration. Fluke photographs were matched in the online photo-ID repository HappyWhale to track individual observation histories and movement records within the islands and on their way to their feeding grounds. Tag attachment periods were relatively short, with transmissions lasting 1.6-12.5 d. Movement behavior models were developed using hidden Markov models; whales in proximity to land were found to remain in area-restricted search or an intermediate behavior state, while whales that moved between islands or offshore tended to transition into directed travel behavior. Movement patterns and routes were similar between animals and across years, particularly when they transited between Kaua’i and O’ahu and began migrating from Ni’ihau to the first seamounts of the northwestern Hawaiian Islands. Dive data were also analyzed in association with the movement behavior. Whales that transited between Kaua’i and O’ahu as well as those in offshore waters conducted repeated series of deep (>100 m) dives only at night, whereas whales that remained in nearshore waters conducted less frequent and less deep dives day or night. These results provide insight into the inter-island movements and behavior of humpback whales while on the Hawaiian breeding grounds as well as where and how their behavior transitioned into migration.