Some Australian marsupials place such a high priority on reproduction that they can go for weeks without sleeping. According to an international study, such a severe lack of sleep could also be the cause of the death of a large number of male voles.
Australian marsupials are gerbil-sized marsupials. They are relatively unique among mammals in that they only mate at a specific time in estrus and only once a year throughout their lives. This time comes approximately every August. Then the male voles are hit with an incessant three-week sex drive: They mate with as many females as possible and then die en masse from exhaustion, Nature News reports.
According to Erika Zaidi, first author of the new study and zoologist at the University of Melbourne, the reproductive period of animals is very short, but at the same time very intense. The lifespan of male voles is usually limited to just one year. Females, on the other hand, live at least a year longer than them and give birth to at least two litters.
Zaidi and his colleagues were interested in finding out where male voles spend time for intense sex in their short lives. To do this, they captured ten males and five females of the species Antechinus swainsonii and place animals of both sexes in a separate enclosure. The team attached activity monitors to the animals’ necks and took blood samples to measure biomarkers.
It turned out that captive male voles moved around the cage much more during the breeding season and slept much less than during the rest of the year. The behavior of female mice did not change as significantly.
On average, the male animals’ sleeping time was about a fifth shorter than usual, and during these weeks one of the male mice studied slept almost half as much as usual. At the end of the breeding season, two males died within a few hours. The remaining eight male mice lost the ability to reproduce.
The team was interested in seeing whether animals also developed a similar sleep debt in the wild. For this, they captured 38 specimens of the species Agile Antechinus before and after the breeding season. In both cases, they measured oxalic acid levels in the mice’s blood. Namely, in case of lack of sleep, the level of oxalic acid in the animal’s blood begins to decrease.
It was seen that during the reproductive period the oxalic acid content in the blood of male mice decreased dramatically. Unlike captive females, oxalic acid levels also decreased in females living in the wild. This suggests that the agile males did not let the opponent’s gut see the mate in full.
Mysterious death
Erika Zaid and coauthors hypothesized that sleep deprivation is primarily responsible for the annual mortality surge in male voles. However, the two men who died during the study were by no means the most ardent vigilantes. According to Zaid, what could be the cause of the animals’ death in this case is not yet clear.
Mammalian psychologist Adrian Bradley of the University of Queensland, who was not involved in the study, assessed the work in depth. The results of the new study correspond to previous findings. In fact, he discovered that during the breeding season, male mice can become so hyperactive that they climb up his legs. Bradley hypothesizes that males’ eating habits change so radically during this period that malnutrition instead becomes fatal for the animals.
In the future, Zaid intends to shed more light on the causes of male death. He hypothesizes that the answer may lie in some environmental factor: for example, a parasite may begin to affect males even before the breeding season begins.
On the same topic, another research article was published in the journal Australian Mammology, which opens up another aspect of mating mortality in marsupials. Namely, the authors saw with their own eyes how a male vole eats his sister who died of exhaustion.
According to the study’s lead author, Associate Professor Andrew Baker, the human eye has never seen such an act of cannibalism in nature. He hypothesizes that after a busy breeding season, surviving males see dead conspecifics as a quick and easy way to obtain energy.
According to Baker, the cause of male mortality could be poor immunity. In addition, the testicles of male voles have developed unusually large: they figuratively pump testosterone throughout the animal’s body. As a result, the animal’s body is no longer able to regulate the level of the stress hormone cortisol. When immunity collapses under high cortisol pressure, any minor injury can be fatal to a mouse.
The study was published in the journal Current Biology.
2024-01-26 09:44:00
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