Less Sleep in Sandpipers Leads to More Offspring: Study

You might not be able to do without sufficient sleep but male pectoral sandpipers can go more than a fortnight with hardly any sleep, the most extreme case of uninduced sleep deprivation known in any animal.

According to the new study that is being published on Thursday in the journal Science, Male pectoral sandpipers sleep less than their counterparts during the bird's intense three-week breeding season mate with more females and sire more offspring - and don't appear to be impaired by their sleeplessness.

This extra ordinary relationship was brought to light by a team of researchers headed by Bart Kempenaers from the Max Planck Institute for Ornithology in Seewiesen.

The researchers with the help of innovative tag monitored the movement of male-female interactions as well as the brain activity in conjunction with DNA paternity testing. The most astonishing fact that they observed is that the most sleepless males were the most successful in producing young.

As the first evidence for adaptive sleep loss, these results challenge the commonly held view that reduced performance is an evolutionarily inescapable outcome of sleep loss.

According to the study, during the three-week mating period male pectoral sandpipers (Calidris melanotos) are active for up to 95 percent of the time. This is even more remarkable considering the fact that the birds have just arrived in their breeding area in Alaska, after migrating from their overwintering grounds in the southern hemisphere.

Pectoral sandpipers have a polygynous mating system where one male mates with several females. Since the males are not occupied with parental care, a male's reproductive success is determined exclusively by his access to fertile females.

"Males have to constantly repel their rivals through male-male competition and simultaneously convince females with intensive courtship display," says director Bart Kempenaers. "Given that the sun never sets during the Arctic summer, males that can engage in this extreme competition 24/7 should be at an advantage."

Paternity was determined by collecting DNA from all males, all females, and all offspring in the study area. Using transmitters attached to the feathers of all males and most females, the researchers were able to tack the bird's activity. These radiotelemetry based senders allowed the team to monitor whether the specie was moving or resting. They even counted the brain recordings and muscle activity which confirmed that active birds were awake and that inactive birds were in fact sleeping. The brain activity recordings also reveal variation in sleep intensity.

"Males that slept the least had the deepest sleep," says co-author Niels Rattenborg who conducts sleep research at Seewiesen. "Although this suggests that the birds might compensate for sleep loss by sleeping deeper, the researchers found that even when this was taken into consideration, the birds were still experiencing a deficit in sleep."

"Long sleeping males may lack genetic traits that enable short sleeping individuals to maintain high performance despite a lack of sleep," argues Bart Kempenaers.

The researchers believe that determining why only some males engage in this adaptive sleeplessness may provide insight into the evolution of this extreme behavior, as well as the ongoing debate over the functions of sleep and its relationship to health and longevity in humans.