Everyone needs sleep. When people or animals don't get enough sleep, they can experience difficulty paying attention, irritability, and other negative effects. However, the Australian antechinus doesn't seem to care as it sacrifices many hours of sleep to have as much sex as possible. Over the course of three intense weeks of breeding season, the males of this small marsupial – a small mouse-like creature – attempt to copulate with the largest number of females possible in sessions lasting up to 14 hours. Researchers at La Trobe University in Melbourne, Australia, have identified this behavior and are publishing their findings this Thursday in Current Biology.
The 13 known Antechina species live mainly in Australia and Tasmania. They have a short lifespan of only 11 months and the males usually die shortly after the mating season. Their unusual life story attracted scientists to study them. Although catching them wasn't easy, animal scientist Erika Zaid and her colleagues recorded the movements and metabolic measurements of 450 of these animals to study their sleep routines. They found that, on average, males sacrificed at least three hours of rest each night during the three weeks that females were in heat.
Zaid explains that the urgency of male antechines is that they are semelparous, meaning they reproduce only once in their lives. On the contrary: females live twice as long and have more opportunities to reproduce. This means they don't want to waste time sleeping and copulating for 12 or 14 hours while storing sperm from multiple males and not having to look for a mate. When a female stops sleeping, it is because of the male harassment she is subjected to during the mating season.
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To ensure their reproductive success, males also physically compete with each other in sperm competition to gain access to as many females as possible. Those who sleep less will be more successful. According to experts, sleep reduction could be adaptive when the need to reproduce is “extreme.”
Death from too much sex?
There are three things all animals must do: eat, not be eaten, and reproduce. The ability to achieve these goals depends on the amount of sleep you get, and the features that rest provides cannot be bypassed. There is no animal that stops sleeping completely, but there are some, such as the antechinus, that prefer reproductive success to sleep. The most extreme case is that of the pectoral sandpiper, which spends up to 15 days without sleep, partly in order to mate with as many females as possible.
However, lack of sleep takes its toll. After the mating season, male antechines developed skin lesions, fur loss and reduced awake performance, “an effect that worsens night after night,” Zaid explains. Other previous research suggests that precisely because of this lack of sleep, antechinas lead short lives, which they call reproductive suicide. But after this experiment, Zaid's team is not entirely unanimous: “Eight out of ten survived the mating season and the two who died at the same time were not the ones who slept the least,” says the author.
Researchers want to learn more about how antechines deal with sleep loss that reaches levels that would cause people to behave as if they were legally drunk. “Are the Antequines equally committed but just carrying on?” they ask. “Or are they simply resistant to the negative effects of sleep restrictions?”
Unfortunately, after all the effort, the offspring of these marsupials don't have it so easy. Females can give birth to up to 18 young, but since they only have six teats to feed them, only a third of them will survive. Although antechines are not endangered species, the loss of their habitat due to human development poses a threat to their survival. The author states that it is very difficult to catch specimens and suspects that the number of them today animals that occur in nature “is not nearly as high as in the 1970s”.
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