Data from: Methods in field chronobiology

Chronobiological research has seen a continuous development of novel
approaches and techniques to measure rhythmicity at different levels of
biological organization from locomotor activity (e.g. migratory
restlessness) to physiology (e.g. temperature and hormone rhythms, and
relatively recently also in genes, proteins and metabolites). However, the
methodological advancements in this field have been mostly and sometimes
exclusively used only in indoor laboratory settings. In parallel, there
has been an unprecedented and rapid improvement in our ability to track
animals and their behaviour in the wild. However, while the spatial
analysis of tracking data is widespread, its temporal aspect is largely
unexplored. Here, we review the tools that are available or have potential
to record rhythms in the wild animals with emphasis on currently
overlooked approaches and monitoring systems. We then demonstrate, in
three question-driven case studies, how the integration of traditional and
newer approaches can help answer novel chronobiological questions in
free-living animals. Finally, we highlight unresolved issues in field
chronobiology that may benefit from technological development in the
future. As most of the studies in the field are descriptive, the future
challenge lies in applying the diverse technologies to experimental
set-ups in the wild. This article is part of the themed issue ‘Wild
clocks: integrating chronobiology and ecology to understand timekeeping in
free-living animals’.