POPULATION REGULATION - A DYNAMIC COMPLEX OF INTERACTIONS

Looking for a single, consistent cause for population regulation is no t only wishful thinking, but also hinders our efforts to understand po pulation dynamics. Population regulation is not only multifactorial, b ut interactions among those factors are important; single-factor exper iments can miss important interactions. In addition, the ecological co ntext 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. Par asitic disease can be an important regulatory factor on its own, but i ndirect effects through interactions with energy budgets or predation are likely to be more important. Disease may act as a precipitating mo rtality factor when energy (and especially protein) budgets are low; u nder such circumstances, disease may be important, but which disease m ay be immaterial. The complex interactions involved in regulation can be understood only by using all of the tools available: field observat ions, field and laboratory experimentation and dynamic modelling.