Marsupial males in fatal attraction
Print Edition
Sex is such a frenetic and stressful process for some male marsupials that it literally kills them — and female promiscuity partly fuels this “suicidal” behavior, according to Australian-led research.
Scientists have wondered for decades why some species of insect-eating marsupials dropped dead after mating.
Now research published in the US-based Proceedings of the National Academy of Sciences puts the “dying off” down to the animals’ extreme efforts to ensure their sperm is successful in the short once-a-year window that females offer to mate.
“There’s always a cost to reproducing — it’s an energy expensive thing,” lead researcher, mammal ecologist Diana Fisher from the University of Queensland, said yesterday.
“But they haven’t spread out their effort over time ... and they just die afterward.”
Organisms that mate once and die are common in plants and fish, but rare in mammals.
Among the exceptions are some species of small marsupials, including the mouse-like antechinus and the phascogales and the dasykaluta, a rodent-like cousin of the antechinus.
Fisher said the male marsupials that die are so intent on mating that their high testosterone levels trigger a cascade effect of stress hormones, which causes the animals’ body tissue to break down and their immune systems to collapse.
“They mate for 12 or 14 hours at a time with lots of females, and they use up their muscle and their body tissues and they are using all of their energy to competitively mate,” she said. “It’s sexual selection.”
The study, which included researchers from the University of Sydney and the University of Tasmania said females escalated sperm competition by synchronizing their mating period and mating promiscuously.
“Precopulatory sexual selection by females favoured the evolution of suicidal reproduction in mammals,” it said.
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