Sudden changes in certain ecological systems, such as fisheries, may result only from the irregular internal dynamics of a population and not from outside influences, says a report in a recent issue of the journal Science by two UC Davis researchers. Set in the context of changing environments, this internal capacity of populations for sudden and unpredictable deviations suggests that certain animal species may be in a more precarious situation than previously acknowledged, says co-author Alan Hastings, chair of the environmental studies division at UC Davis. Hastings compares the changes to a spinning top that suddenly may begin wobbling for a while and then regain its regular spin on its own. These wobbling transient dynamics may hold the key to understanding and managing ecological resources, he says. The model builds upon a way of understanding the complex patterns of nature through the simple nonlinear mathematics popularly known as "chaos."