Birds that breed successfully in continuous Arctic daylight may challenge the view that decreased performance is a universal outcome of sleep loss.

A study published today in the journal Science may provide insight into the ongoing debate over the functions of sleep and its relationship to health and longevity in humans.

Researchers, including co-author Postdoctoral Research Fellow Dr John Lesku of The University of Western Australia, studied a population of shorebirds from the time the females were fertile until they were incubating eggs.

Their multi-year study found that shorter-sleeping male pectoral sandpipers (so called because of distinctive chest markings) are more attractive to females than those that sleep more.

Dr Lesku said the research was important because it questions assumptions about sleep, including that a fixed amount of daily sleep is needed to maintain high performance.

Dr Lesku, who is in UWA's School of Anatomy, Physiology and Human Biology, is an international expert in the function, ecophysiology and evolution of sleep.  In another of his many papers, he compares the sleep of ostriches to that of platypuses.

In his most recent paper, "Adaptive Sleep Loss in Polygynous Pectoral Sandpipers", working with colleagues at the Max Planck Institute for Ornithology - Seewiesen, University of Zurich/ETH Zurich and e-obs GmbH in Germany, they showed that male sandpipers are able to maintain high neurobehavioural performance despite greatly reducing their sleeping time during a three-week summer period of intense male-male competition for access to fertile females. Males that slept the least sired the most offspring.

Dr Lesku said in humans and other mammals, sleep restriction and fragmentation diminish attention, motivation, sensory-motor processing and memory with often adverse consequences for the individual and society.  This suggests that sleep performs essential restorative processes.

However, an alternative view suggests that sleep may simply be a state of adaptive inactivity that conserves energy when activity is not necessary.

In some species, if a promiscuous male is to maximise his reproductive fitness, he must successfully engage in competitive displays and physical fights with other males and in courtship displays with females.  A male's reproductive success is strongly related to the proportion of time he displays territorial or courtship behaviour.

"While pectoral sandpipers may have delayed full recovery sleep until the breeding season finished, their ability to postpone this potential recovery for up to three weeks while maintaining high neurobehavioural performance is unprecedented," Dr Lesku said.

Media references

Postdoctoral Research Fellow Dr John Lesku  (+61 8)  6488 3312
(UWA School of Anatomy, Physiology and Human Biology)
Director, Dr Bart Kempenaers (Max Planck Institute for Ornithology  (+49) 8157 932 334
- Seewiesen, Germany, Department of Behavioural Ecology and Evolutionary Genetics
Michael Sinclair-Jones (UWA Public Affairs)  (+61 8)  6488 3229  /  (+61 4) 00 700 783