POPULATION REGULATION - A DYNAMIC COMPLEX OF INTERACTIONS

Looking for a single, consistent cause for population regulation is not only wishful thinking, but also hinders our efforts to understand population dynamics. Population regulation is not only multifactorial, but interactions among those factors are important; single-factor experiments can miss important interactions. In addition, the ecological context constantly changes, so that regulatory processes trade a moving target; experiments can have different results if the context differs. I focus on interactions among nutrition, predation and parasites. Parasitic disease can be an important regulatory factor on its own, but indirect effects through interactions with energy budgets or predation are likely to be more important. Disease may act as a precipitating mortality factor when energy (and especially protein) budgets are low; under such circumstances, disease may be important, but which disease may be immaterial. The complex interactions involved in regulation can be understood only by using all of the tools available: field observations, field and laboratory experimentation and dynamic modelling.