Coordinated movements of multiple pied-billed grebes in association with an American alligator

Abstract

Interspecific associations can arise when one species benefits from the presence or behavior of another, often during foraging. Here, we describe a previously undocumented behavioral interaction between pied-billed grebes (Podilymbus podiceps) and an American alligator (Alligator mississippiensis) in a freshwater wetland in South Florida. Across a ~10-min observation period, two grebes consistently followed behind an alligator, adjusting their speed and trajectory in concert with its movements and maintaining close spatial proximity. Although the grebes approached the alligator closely and repeatedly followed its trajectory, one bird exhibited a rapid escape response when the alligator turned and approached directly, indicating an active assessment of predation risk. This behavior aligns with nuclear follower foraging associations in other taxa, where follower species exploit prey flushed by a larger nuclear species. While grebes are not currently known to form such associations, this instance suggests that they may opportunistically do so, such as under favorable ecological conditions. The observation contributes to a growing body of work recognizing the ecological significance of facultative interspecific associations in shaping foraging behavior and predator–prey dynamics. We discuss possible explanations for the behavior and its placement within interspecific interaction frameworks.