“Information-mediated Allee effects in breeding habitat selection”

Posted on by Owen

Kenneth A. Schmidt, Jacob Johansson, and Matthew G. Betts

Insufficient ‘information providers’ as cues for habitat use can promote information-mediated Allee effects

Declines in social information use can hasten extinction in small and shrinking populations

Unbanded veery (Catharus fuscescens).
Watercolor painting by Natasja van Gestel, PhD (© 2005).

The presence, activities, and performance of one’s neighbors are a fundamental source of information: where to forage, choosing a breeding site, and avoiding predators. This social information, together with personal experience, can increase an individual’s reproductive success and survival—even in otherwise nonsocial organisms. However, such behavior may also hinder conservation efforts for species and populations that are already small or in decline. Such populations have fewer information providers—i.e., individuals to copy from or eavesdrop on concerning their success or activities. This decline in social information could reduce the efficiency of finding good habitat, food, or shelter, in turn driving populations into even more rapid rates of decline.

An example of a putative prospecting event. The photo shows an unbanded veery (Catharus fuscescens) visiting a neighbor’s nest after a predation event. Prospecting for visual and vocal signs of a neighbor’s breeding success or failure can influence future choices of where to breed, and lead to higher reproductive success.
(Credit: Kenneth A. Schmidt)

Kenneth Schmidt (Texas Tech University) and colleagues Jacob Johansson (Lund University) and Matthew Betts (Oregon State University) explore this hypothesis in their article appearing in The American Naturalist using a mathematical modeling approach. They find strong evidence for such positive feedbacks at low population densities—which they term a “socially mediated Allee effect” (an Allee effect refers to negative impacts on a population that occur at small population sizes). The population-level effects of social information behavior may partly explain why small populations of animals tend to be at greater risk of extinction (in addition to other factors such as inbreeding).