Arctic Barnacle Geese Research

The daily or seasonal release of hormones is essential for synchronising biochemical, physiological or behavioural processes. Different hormones interact with each other at various levels; therefore, examining only one hormone separately will lead to an incomplete picture. No single hormone has a one-to-one relationship with any particular behaviour, and neither is any behaviour regulated by only one hormone. One main goal here is to gain a more complete understanding of the relationships between three rhythmic hormones and their influence on daily and seasonal activity at the individual level. This is highly relevant as mistimed biological clocks or deviations of a body’s own rhythm may cause health problems. 

As the major product of avian clocks, melatonin controls the sleep-wake cycle and other daily activities (feeding, rest) along with seasonal activities (e.g. hibernation, moult, migration and reproduction). The release of melatonin is controlled by daily changes of light and darkness: light causes an inhibition, but darkness triggers secretion, resulting in increased levels. Finally, melatonin triggers the regulation of other rhythmic hormones, such as prolactin and corticosterone. Besides other functions, all three hormones are released during the stress response, an elemental physiological task. The relationship between melatonin and the light-dark cycle is clearly defined in temperate latitudes, but above the Arctic and below the Antarctic circle (66°N/S), where 24-hours of daylight prevail in the summer, but 24-hours of darkness in the winter, this relationship is less clear, but it is fascinating for studying the effects of time and rhythmical phenomena of life processes.