| Summary: | Animal signals convey information intra- and interspecifically, but their adaptive importance is often unknown. The humpback whale (Megaptera novaeangliae) is a widespread, highly vocal cetacean known to produce both songs and non-song calls, the latter of which has been less-studied. While associations between non-song calls and behaviour have been examined throughout their range, additional investigations into their temporal patterns in understudied regions may further provide information as to their behavioural context. Using continuous 24-h passive acoustic monitoring and aural/visual surveys of recordings, I investigated the temporal patterns in non-song call activity within three broad classes (low frequency, high frequency and pulsed) on a diel and daily scale across three summers (July-August, 2015-2017) at a foraging site on the northeast coast of Newfoundland, Canada. Low frequency calls were the dominant call class (43-75%) across all time scales relative to high frequency (9-17%) and pulsed calls (8-40%), suggesting low frequency calls are vital for communication among humpback whales on the foraging grounds, as observed throughout their range. Non-song call activity in all call classes was higher during light relative to dark or twilight periods, suggesting individuals are inactive, not engaged in behaviours requiring acoustic communication, and/or remain silent to minimize predator detection. Call activity peaked when humpback whales arrived into the study area and subsequently decreased, suggesting calls are more important in mediating social interactions during movement into the area, but less-so as whales disperse to forage throughout the area. Lastly, call activity varied among years with 2016 having double the call activity of the other years, which was also associated with the highest estimated humpback whale abundance but lowest prey (capelin, Mallotus villosus) biomass, suggesting call activity may indicate humpback whale abundance. Overall, temporal call activity patterns suggest that ...
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