This note focuses on bubble rings, a unique and sparsely documented genre of bubble features produced by baleen whales, although well-described among odontocetes, including Atlantic bottlenose dolphins (Tursiops truncatus, McCowan et al. 2000), beluga whales (Delphinapterus leucas, Hill et al. 2011), and Orinoco dolphins (Inia geoffrensis, Gewalt 1989). Not to be confused with a bubble net (spiral-shaped fish trap, a ring is a poloidally spinning, air-infused vortex. At Stellwagen Bank in the North Atlantic Ocean, Payne (1995) described them as “madly spinning doughnut-shaped clouds that look like giant smoke rings about three feet in diameter that rise rapidly to the surface.” Payne opines on their frequency, noting: “Only one particular whale has been known to engage in this activity, and even she seldom does it. However, once she gets going, the process becomes obvious and is done vigorously.

Here we report on 12 ring-production episodes involving 39 bubble rings produced by 11 individual humpback whales. The aim of this research is to describe contexts in which humpback whales produce bubble rings and provide insights into their potential functions. We examine evidence for Payne's (1995) hypothesis that bubble rings are associated with foraging as defined by being produced in the presence of prey and feeding activity (vertical lunges, open mouths, extended ventral pleats). Next, we examine the hypothesis that rings are associated with social aggression, as proposed for wild spotted and bottlenose dolphins (Herzing 1996, 2000; Pryor 1990; Pryor and Kang 1980). We use Baker and Herman's (1984) and Pitman et al.'s (2017) definition of aggressive behavior in humpback whales, which includes high levels of arousal, wheezed blows, trumpet blows, slashing of the tail and flippers, and charges directed toward antagonists (e.g., male rivals, killer whales [Orcinus orca]). We also examine whether rings are linked to inquisitive behavior in which whales approach boats and swimmers (Mangott et al. 2011; Swartz 2018). Finally, using drone observations collected by several private investigators, we searched for ring production in the absence of boats and close human presence.