A study conducted by scientists at the Max Planck Institute for Ornithology in Seewiesen, Germany has shown that the male members of a sandpiper population who spend less time sleeping are more successful at mating with females and have more offspring.
The sandpiper mating season takes place during the summer in the Arctic Circle, when the sun practically never goes down. Males of the species compete to impress females by fighting with each other, defending territory, and flying over the females while making a hooting sound.
The study, published in Science magazine, was meant to explore the hypothesis that sleep can be accounted for evolutionarily as a means of conserving energy at times when it is not needed. During times when high levels of performance and stress are required, such as mating season, the clear adaptive advantage goes to those organisms who sleep less. Therefore, regular sleep might not be considered as important as strategically timed sleep.
The Planck Institute scientists used electroencephalogram and electromyogram dataloggers to record the amount of time each bird was sleeping during the endless days. Sleep time ranged from 2.4 to 7.5 hours.
Birds who slept less were more successful at interacting with females, achieving coitus and passing on their genes by conceiving their young. Interestingly, these birds were also more likely to have returned (and thus to have survived) the following year, meaning there was no measurable effect of low sleep on their overall health.
However, that’s not to say there is no cost to sleep deprivation. The mating period is a relatively short 3-week window, and it may be possible that these birds were catching up on their sleep at a later time. The important ramification, however, is that sleep is not desirable at a time when an animal has some higher survival-related or reproductive priority.
– By Amanda Watson