World Wide Eyes: Social Media-Assisted Wildlife Research. Assessing Supplementary Feeding Areas for Eastern Australian Humpback Whales as a Case Study.
Humpback whales typically adopt a "feast-and-famine" strategy, feeding intensively at high-latitude summer feeding grounds while fasting throughout migration. However, increasing reports of feeding at mid-latitudes suggest that some individuals may supplement their energetic requirements along migratory corridors. Detecting and monitoring these emerging behaviours remains challenging because conventional marine mammal surveys are often spatially and financially constrained. Here, we used passive citizen science by systematically compiling humpback whale feeding records from publicly shared Facebook and Instagram posts and the citizen-science platform Happywhale to investigate feeding events of the Eastern Australian population over five consecutive migration seasons (2020-2024). A total of 256 feeding records were collected, revealing three recurrent candidate Supplementary Feeding Areas (SFAs): the Sapphire Coast (New South Wales), Port Phillip and Bass Strait (Victoria), and southeast Tasmania. Feeding events occurred across multiple migratory months, involved both solitary whales and groups, and included both krill and schooling fish as prey, with lunge feeding representing the predominant feeding strategy. Comparison of passive and active citizen-science sources showed that social-media records substantially increased the number of documented feeding events and more frequently allowed feeding behaviour to be identified. The temporal recurrence of feeding events across five consecutive migration seasons supports the hypothesis that some behaviours traditionally interpreted as opportunistic feeding may instead represent recurrent supplementary feeding. Overall, this study demonstrates the value of passive citizen science as a cost-effective complement to conventional monitoring programmes for detecting large-scale behavioural changes and identifying candidate supplementary feeding areas in migratory humpback whales.