by For some, happiness is getting enough sleep. But for a small marsupial in Australia, sex is a higher priority than getting some shut-eye – and he is willing to sacrifice hours of every day to reach his happy ending.
Australian-based scientists found that mouse-sized male antechinus trades more time for reproductive activities during the mating season, with one monitored male cutting his sleep time in half during that period.
The study, published Thursday in the journal Current Biology, is the first to show direct evidence of this type of “extreme” sleep restriction in any land-dwelling mammal, according to the researchers.
“Animals have to reproduce to pass on their genes, but they also have to sleep to survive,” Erika Zaid, lead author and animal behavior researcher at La Trobe University in Melbourne, told CNN.
“Long-lived animals like humans and elephants don’t have this pressure to reproduce in a short period of time. It is their choice to be able to sleep as long (as) they want (and) every day,” she said.
Unlike their female counterparts, male antechinus are semelparous, meaning they can only breed once in their lifetime, making long sleep a luxury that can cost them their passing on genes, explained Zaid. A non-breeding dusky antechinus spends an average of 15.3 hours sleeping, according to the researchers.
“Sleep restriction in breeding male antechinus is likely an adaptive behavioral response driven by strong sexual selection,” the paper said. This drives them to compete with other males to reproduce with as many females as possible, before dying soon after their first – and last – mating season.
To study the semelparous marsupials, researchers examined two species of antechinus: dusky antechinus (Antechinus swainsonii) and wild agile antechinus (Antechinus agilis) both in captivity and in the wild.
Researchers found that males from both species were not only more active during the mating season, but also slept less during the same period.
Data showed that males slept three hours less per night, every night, for three weeks – roughly the length of the mating period. Males, which only live for 11 months, reproduce once in their lives before dying and females can reproduce more than once, Zaid said.
Sleep is an “essential and seemingly universal behavior in the animal kingdom,” said John Lesku, associate professor of zoology at La Trobe University and a sleep scientist, who was involved in the study.
“Sleeping three hours less per night affects waking performance in humans, (although) antechinus did this for three weeks. Thus, antechinus may be resilient to sleep loss and have an unknown mechanism to cope with less sleep during this time, or they may accept the physiological costs of staying awake for paternity to get before they die,” Lesku told CNN.
The paper suggests that reproductive pressures on the males during their only breeding season led to decreases in sleep, with increased sexual activity positively associated with increases in testosterone, the male sex hormone, during the same period. time.
Women are also sleep deprived
Using accelerometers — instruments used to measure the acceleration of a moving body — the researchers tracked the movement of 15 dusky antechinus (10 males) before and during the mating season.
Researchers took blood samples to measure any changes in hormones and took electrophysiological recordings from four males to measure how much they slept.
Blood samples were also taken from 38 wild agile antechinus (20 males) to see if oxalic acid, a biomarker for sleep loss, decreased during the mating period.
Although the decrease in oxalic acid suggests that the agile antechinus was sleep deprived during the mating season, the results show that the difference between males and females was not significantly different, which Zaid suggests may which would suggest that females in the wild are as sleep deprived as males. harassment during the mating period.
“Our study is the first to compare the activity levels of males and females before, during, and after the breeding season, and to reliably link rest with sleep using accelerometry, electrophysiology, and metabolism ,” researchers said in the paper.
Volker Sommer, professor of evolutionary anthropology at University College London, told CNN: “This seems to be an old pre-breeding trick of not letting one’s guard down: men are forced to stay awake because so do their competitors.” Sommer was not involved in the study.
Although the results do not indicate a cause of death in the post-breeding male, there are several possibilities, such as elevated corticosteroids – steroid hormones – and sleep deprivation.
Lesku said researchers would like to examine how male antechinus cope with restricting their sleep for three weeks.
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