FREE Physics Lecture * Wed, Mar 30,5:30 * Wheeler Opera House

Heather Lynch, Stony Brook University
“How Satellites Reveal the Physics of Penguins”

Aggregations are common in ecological systems at a range of scales and may be driven by the underlying landscape in which animals are living or by interactions among individuals. One mechanism leading to ‘self-organized’ animal aggregations is captured by Hamilton’s “selfish herd” hypothesis, which suggests that aggregations may be driven by an individual’s effort to minimize their risk of predation by surrounding themselves with other animals of the same species. Using data captured by satellite imagery and unmanned aerial vehicles (UAVs), we demonstrate that aggregations observed in penguin colonies stem from the delicate interplay between risk avoidance strategies within the population and the landscape terrain in which these dynamics play out. Unlike other animal groups where dynamics are highly fluid (such as bird flocks and fish schools), penguins are highly faithful to individual nest sites; as a result, penguin colonies can become trapped in suboptimal arrangements in which many penguins are stuck breeding on the colony’s edge where their nests are vulnerable to predation. The resulting spatial dynamics are responsible for a hysteretic response to long-term changes in abundance in which even temporary declines in abundance from one year to the next leads to greater fragmentation of the colony, which precipitates further declines. Remarkably, the spatial signature of this process allows us to differentiate a colony that is increasing from one that is decreasing based on spatial pattern alone, which provides even greater insight about the health of colonies captured by satellite imagery. By linking penguin biology with landscape hydrology, geology, and terrain morphology, this work provides a link between current spatial patterning and past dynamics and provides a stark warning about the possibility of critical collapse in populations of these iconic Antarctic species.