Keeping track of the seasons

Animals display a striking diversity in patterns of seasonal behaviours, such as reproduction, migration, hibernation, and moult. Annual cycles differ among species, but also among individuals within species, in the timing and duration of each life-history stage and in the relative flexibility of their annual schedules. Simultaneously, habitats are diverse with respect to seasonality, especially in the extent of their inter-annual variation and the predictability of this variation. This predictability of seasonal change is an important characteristic of the environment, as, in order to match their behaviour to the seasons, animals need to predict the optimal time for each life-history stage to complete necessary changes in physiology in advance. In view of this diversity in both species’ behaviour and habitats, researchers have developed different approaches to study annual cycles. Over recent decades significant progress has been made independently in two pertinent disciplines, ecology and physiology. This research has shown that various environmental and endogenous cues are used as time keeping mechanisms. The use of these cues differs between related taxa, and sometimes even within species, depending on the ecological setting. Therefore, close collaboration between ecologists and physiologists is crucial for a more complete understanding of annual timing. Research progress is however hampered because the various approaches are not well integrated. General views converge, but controversy persists about model ideas and the relative contribution of different external and internal factors to seasonal timing. This is unfortunate, especially because understanding seasonal behaviour has become an urgent issue in our times of rapid global climate change. Many species have altered their seasonal timing due to increased temperatures but it remains to be determined whether these shifts occur at a rate fast enough to match the changes in environment.

Our aim at the Lorentz Centre workshop is to gain a fuller understanding of seasonal timing by integrating disciplines, bringing ecologists and physiologists together. We hope to develop a common framework and to lay out a road map for future research to understand timing under different ecological conditions. We envisage that the convenors, together with some of the key-participants, will produce a review paper both summarizing the state of the art in the field and outlining the road map for future research. A complementary goal of the workshop is to compare and contrast seasonal timing of mammals and birds. Birds share many problems of, and possibly solutions for, seasonality with mammals, the only other group of endotherms. Mammalian scientists have studied similar questions, but collaboration between researchers working on the two vertebrate groups has been minimal. There is potentially much to be gained from a forum that engenders an exchange of experiences and current ideas between avian and mammalian researchers.