Semelparity in a large marsupial

Complete mortality of males after mating is known in several small dasyurid and didelphid species (up to 300 g) and has previously been suggested to be a consequence of their small size and their inability to sequester sufficient fat reserves for an intense rut in the winter. Males of these species use increased corticosteroid levels to allow protein catabolism, enabling them to support their mating effort with other body reserves. However, increased corticosteroid levels have negative consequences such as anaemia, gastrointestinal ulceration, immune suppression and disease. The Australian dasyurid Dasyurus hallucatus shows complete male die off after mating in tropical savannah, yet males of this species may weigh as much as 1120 g and continue to eat during the rut. Die off in D. hallucatus shows many similarities to that in the smaller species including weight loss, fur loss, parasite infestation, increased testosterone levels and anaemia. However, in contrast to smaller species, there is no evidence of elevated corticosteroid levels or gastrointestinal ulceration. Consequently, the phenomenon of male die off after mating lacks a universal explanation.