Marsupial species evolved “suicidal reproduction”

Male survival after mating is pretty dismal for this species

Monash.edu

Many animal species consist of members that will only mate once before dying. This reproductive strategy, often seen in fish and insects, can make evolutionary sense when the species is able to produce a lot of offspring from that single mating. Given that salmon can release thousands of eggs when they spawn, a single mating can produce a lifetime's worth of offspring.

That's not true for mammals, though. Raising young internally limits the number you can produce from a single mating, while the extensive post-natal care required by mammalian young ensures that the female has to stick around for a while after giving birth. But males don't always participate in postnatal care, so it probably shouldn't be a surprise to learn that there are mammals out there that engage in what researchers are terming "suicidal reproduction." The problem is that the behavior only occurs in a small number of marsupial species, and researchers have been arguing for 30 years about why that is the case. Now, some Australian researchers have come up with an answer: a combination of sperm competition and promiscuous females.

The marsupials that engage in this "one strike and you're out" approach to mating all die off because of a general immune failure that happens shortly after mating. This has nothing to do with the process of mating itself; in fact, it starts well in advance of mating, as the males build up a store of sperm and then permanently shut their gonads down. The question wasn't so much how the males' death takes place, but why. What sort of evolutionary advantage could this provide?