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Pirotta, V., Taylor, I. A. R., Harcourt, R., & Reidenberg, J. S. (2026). Gaping in humpback whales, a unique behavior documented through citizen science. Animal Behavior and Cognition, 13(2), 153-164.  https://doi.org/10.26451/abc.13.02.03.2026

Humpback whales (Megaptera novaeangliae) are arguably the most frequently observed whale species in the world. Their coastal habits, tolerance of boats, and rapid recovery post-whaling has resulted in this species dominating whale-watching vessel operations and in-water swim-with tourism in all major ocean basins. Observations by tourists, i.e., citizen scientists, are often shared via social media providing an opportunity to document otherwise rarely seen whale behavior. We present evidence gathered through citizen science via social media of gaping by humpback whales. Gaping is a common form of behavior in many animals, wherein an animal opens its mouth widely, displaying the interior, but it may have various functions. Gaping is therefore defined by form, and here we refer to gaping not associated with feeding and observed only outside known feeding areas. A desktop search of the internet returned a total of 66 social media observations of gaping collected from vessels (gaping above water, n=36), from swim-with operations (gaping fully submerged, n=24, including jaw popping – clapping of their mouth with the production of a sound); and from drone observations (n=6). We suggest several possible interpretations including; 1) playful/social behavior and communication; 2) general jaw stretching and post/pre suckling (calves only); 3) playing with debris (calves only), and 4) natural separation of mandible (due to gravity) as a result of surface-active behaviors, e.g., chin slapping/head lunging - picked up from the search. This paper further illustrates how citizen science and social media can document rarely seen whale behavior.

Humpback whale, Tourism, Citizen science, Gaping, Mouth open, Behavior, Megaptera novaeangliae