Methods in field chronobiology

Abstract

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.

Nightly selection of resting sites and group behavior reveal antipredator strategies in giraffe

“…For further investigations on the entire nocturnal behavior of wild giraffe, it would be useful to apply GPS tracking units including an accelerometer which have been used successfully for African elephants, sloths ( Bradypus variegatus ; Bradypus pygmaeus ) and cows ( Bos taurus ) (Fukusawa, Komatsu, Higashiyama, & Oshibe, ; Soltis, King, Vollrath, & Douglas‐Hamilton, ; Voirin et al, ). However, this technology is expensive and unless each individual of a group is equipped with a data logger, analyzing group behavior and group dynamics is impossible (Dominoni, Åkesson, Klaassen, Spoelstra, & Bulla, ). Especially for giraffe living in discontinuous bonds (fission–fusion), attaching units to all individuals in any given group is not expedient to investigate social preferences or guarding behavior.…”

“…Bulla, 2017). Especially for giraffe living in discontinuous bonds (fission-fusion), attaching units to all individuals in any given group is not expedient to investigate social preferences or guarding behavior.…”

Two sides of a coin: ecological and chronobiological perspectives of timing in the wild

“…The increasing appreciation of ecology by chronobiologists stems from acknowledging the complexity of the circadian system, but also from realizing that richer ecological contexts produce unexpected results. For these and other advances, chronobiologists who study Wild Clocks can benefit from the surge of data that are collected by powerful animal-tracking technology, and from technical developments that allow more integrative ways to capture chronotype, for example, by remote collection of data on body temperature [74,207,208].…”

Artificial light at night as an environmental pollutant: An integrative approach across taxa, biological functions, and scientific disciplines

“…Although evidence is accumulating for light pollution to alter sleep behavior, and nocturnal rest, the physiological basis for such changes is unknown. Advances in biologging of sleep (Lesku et al, 2012) offer exciting perspectives, especially if integrated with on-board recording of activity and light exposure (Dominoni, Åkesson, Klaassen, Spoelstra, & Bulla, 2017).…”