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Competition drives marsupial males to suicidal sex

Competition drives marsupial males to suicidal sex

New Scientist

Image: Tim Collins Tasmania

Male marsupial mice just don’t know when to stop. For Antechinus stuartii, their debut breeding season is so frenetic and stressful that they drop dead at the end of it from exhaustion or disease. It may be the females of the species that are driving this self-destructive behaviour.

Suicidal breeding, known as semelparity, is seen in several marsupials. This is likely linked to short breeding seasons and the fact that the marsupial mice only breed once a year. It is not clear why this is, but it may be that females can only breed when the population of their insect prey reaches its peak. A year is a long and dangerous time for a small animal, so under these circumstances males might do best to pump all their resources into a single breeding season.

To test this idea, Diana Fisher of the University of Queensland in St Lucia, Australia, and her colleagues tracked how insect abundance changed with the seasons in the marsupials’ home forests. Sure enough, they found that the marsupials’ breeding seasons were shortest where insect abundance followed a predictable annual pattern.

But the insects are not the whole explanation. It turns out that females do sometimes survive the year and breed again. So why do the males always die? Read more on…