Everyone needs sleep. When humans or animals do not get enough sleep, they may have difficulty paying attention, experience irritability, and other negative effects. The Australian antechinus, however, does not seem to care, as it sacrifices hours of sleep to have as much sex as possible. Over the course of the three intense weeks of the breeding period, the males of this small marsupial – a small mouse-like creature – seek to copulate with the greatest number of females in sessions of up to 14 hours. Researchers from La Trobe University in Melbourne (Australia) have identified this behavior and publish their findings this Thursday in Current Biology.
The 13 known species of antechina live mainly in Australia and Tasmania. They have a short lifespan of only 11 months and males usually die just following mating season. Their unusual life history was what attracted scientists to study them. Although catching them was not easy, Animal Sciences researcher 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 antechinuses lies in the fact that they are semelparous, that is, they reproduce only once in their lives. On the contrary, females live twice as long and have more opportunities to reproduce. This means that they do not want to waste time sleeping and copulate for 12 or 14 hours, while they store sperm from multiple males and do not need to look for a mate. If a female stops sleeping, it will be because of the male harassment she suffers during the mating season.
To ensure their reproductive success, in the sperm contest, males also compete with each other physically to access as many females as possible. Those who sleep less will be more successful. According to experts, sleep reduction might be adaptive when the need to reproduce “is extreme.”
Death from too much sex?
There are three things that all animals must do: eat, avoid being eaten, and reproduce. The ability to meet those goals depends on the amount of sleep you get, and the functions that rest provides cannot be circumvented. There is no animal that stops sleeping completely, but there are some, such as the antechinus, that prefer to ensure reproductive success rather than sleep. The most extreme case is that of the pectoral sandpipers, which spend up to 15 days without sleeping, also to copulate with as many females as possible.
Lack of sleep, however, takes its toll. After the mating season, male antechina developed skin lesions, fur loss, and decreased performance when awake, “an effect that worsens night following night,” Zaid explains. Other previous research has proposed that antechinas live short lives, precisely because of this lack of sleep, in what they call reproductive suicide. But following this experiment, Zaid’s team does not completely agree: “Eight out of ten survived beyond the mating season and the two who died synchronously were not the ones who slept the least,” says the author.
Researchers want to learn more regarding how antechinans handle sleep loss, which reaches a level that would cause people to act as if they were legally intoxicated. “Are the antequines equally committed, but they just keep going?” they ask. “Or are they simply resistant to the negative effects of sleep restriction?”
Unfortunately, following all the effort, the offspring of these marsupials do not have it so easy. Females are capable of giving birth to up to 18 young, but since they only have six teats to feed them, only a third of them will survive. Antechinans are not listed as an endangered species, but habitat loss due to human development does represent a threat to their survival. The author details that it was very difficult to catch specimens and suspects that the number of animals present in nature today “is not close to that recorded in the 1970s.”
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