Sleep research goes wild: new insights on sleep homeostasis from studies in geese

All mammals and birds appear to spend a large part of their life asleep; yet, the function of this enigmatic behavior and physiological state remains unknown.

Surprisingly, field studies to examine sleep under the natural conditions where it evolved have so far been exceptionally rare.

In fact, in most ecological studies that assess behavior in the wild, sleep episodes are often little more than blanks in the activity recordings.

However, if sleep indeed serves important functions, then the time available for sleep may be a determining factor in the fitness of an individual.

It is only with recent miniaturization of technology for recording of brain activity that sleep can be studied in free-living animals without affecting their natural behaviour.

We will exploit this technology to study sleep in barnacle geese which display extreme variation in timing and amount of activity across the annual cycle.

During some phases the time for sleep appears to be limited, particularly during the breeding season and during long-distance migration. In all experiments, geese are equipped with EEG electrodes connected to dataloggers for recording of brain activity.

These recordings allow us to assess how varying ecological demands affect sleep duration, distribution of specific sleep stages, and sleep homeostasis.

We will also be able to assess whether migrating birds during non-stop long-distance flights display unihemispheric sleep, i.e., fulfill the need for recovery by alternating sleep between the two brain hemispheres. Together these studies will provide unique insights in the ecology of sleep under natural conditions.