| Summary: | Humpback whales are remarkable for the behavioural plasticity of their feeding tactics and the diversity of their diets. Within the last decade at hatchery release sites in Southeast Alaska, humpback whales have begun exploiting juvenile salmon, a previously undocumented prey. The anthropogenic source of these salmon and their important contribution to local fisheries makes the emergence of humpback whale predation a concern for the Southeast Alaska economy. Here, we describe the frequency of observing humpback whales, examine the role of temporal and spatial variables affecting the probability of sighting humpback whales and describe prey capture behaviours at five hatchery release sites. We coordinated twice-daily 15 min observations during the spring release seasons 2010–2015. Using logistic regression, we determined that the probability of occurrence of humpback whales increased after releases began and decreased after releases concluded. The probability of whale occurrence varied among release sites but did not increase significantly over the 6 year study period. Whales were reported to be feeding on juvenile chum, Chinook and coho salmon, with photographic and video records of whales feeding on coho salmon. The ability to adapt to new prey sources may be key to sustaining their population in a changing ocean. Chenoweth et al 2017. Roy_Soc_Open_Science.RR Code for the calculation of most in-text results, Tables 1 and 2 and the production of Figure 3.Chenoweth et al 2017. Roy_Soc_Open_Science.RBehaveNewData2This dataframe includes the combinations of predictors necessary for creation of Figure 3. The models created by Chenoweth_et_al_2017_Roy_Soc_Open_Sci.R provides the predicted probabilities of humpback whale sighting based on these predictors.HatcheryObsThis dataframe provides observations from all five hatchery release sites over six years. The raw data has been filtered as described in the methods section of the manuscript.Releases.SumThis dataframe provides the Julian Day of the first and last releases ...
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