Subtropical antechinus … males die after sex. Photo: Daniela Parra Faundes
Subtropical antechinus … males die after sex. Photo: Daniela Parra Faundes
8 October 2013

Scientists from The University of Queensland are the first in the world to discover why programmed suicidal reproduction is likely to occur in mammals.

Dr Diana Fisher from the School of Biological Sciences has led research into why some small insect-eating marsupials such as antechinus escalate stress hormones during the breeding season, which leads to total immune system collapse, haemorrhaging, infections, and death after mating in all males.

“These species experience extreme sexual behaviour," Dr Fisher said.

"Mating can go for 12 or 14 hours at a time and they have lots of partners. They use up all possible energy and body tissues on competitive mating, which causes synchronised death after mating in males.

"Males stop making sperm before the mating season and their testes disintegrate, so they are not even using energy on that during the mating period.

"But they can never reproduce again even if they do live.

“People often think that males are sacrificing themselves to leave more food for the next generation, but that isn’t the reason for male die-off.

"It’s not altruism but sexual selection.

"We looked at about 50 species of insect-eating marsupials in South America and Papua New Guinea as well as Australia with a range of male survival, and we found that males of species with low survival or the extreme of suicidal reproduction have short mating seasons.

"Females synchronise reproduction to coincide with a predictable spike in food once a year in higher latitudes where these species live.

"Young weaned at this time are most likely to survive.

"Mating is timed so males must squeeze all of their effort into a short time and space, and they compete fiercely.”

The research shows the importance of climate, and resolves the mechanism of sexual selection responsible.

"Males compete not by fighting, but by mating themselves to death because their sperm is in competition with the sperm of many other males," Dr Fisher said.

"Species with die-off have the largest testes.

“Sperm competition means that males with larger testes and better endurance succeed.

"Females not only benefit by weaning their young when there is most food, but also by promoting this extreme sperm competition, because the highest quality males father their young,” said Dr Fisher.

Media: Dr Diana Fisher, UQ School of Biological Sciences ARC Research Fellow, +61 7 3346 9004 or +61 43 506 6011,

The research paper can be obtained from: Tracey Franchi, UQ School of Biological Sciences Communications Manager, +61 7 3365 4831,

About the UQ School of Biological Sciences
Through research undertaken in the School, UQ has been ranked by the 2012 National Taiwan University Rankings in the top five universities globally for research in ecology and environmental biology and in the top 18 universities globally for plant and animal biology. The UQ School of Biological Sciences attracts researchers of world standing in a range of disciplines, with international leaders in many diverse fields. Our work spans the scales of biological organisation, from molecules and cells to organisms, populations, species and communities. With more than 150 researchers working in evolution, global change biology, ecology, aquaculture, animal behaviour, physiology, entomology, zoology, botany, genomics, development and conservation biology, our researchers and graduate scientists are well-equipped to make a real difference in contributing to solving global problems.