Semelparity in a large marsupial

Abstract

Complete mortality of males after mating is known in several small dasyurid and didelphid species (up to 300g) 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.

Does the degree of endocrine dyscrasia post-reproduction dictate post-reproductive lifespan? Lessons from semelparous and iteroparous species

“…The upregulation of glucocorticoids during the estrous cycle, pregnancy, and lactation also supports a critical role for these steroids in reproductive success (Fanson et al 2014). This post-reproductive corticosteroid response also is seen in humans later in post-menopause (Rozenberg et al 1988), and has been postulated as the cause of death in other semelparous species such as the dasyurid and didelphid marsupials (Fisher et al 2013;Fisher et al 2006;Oakwood et al 2001;Schmidt et al 2006). However, in contrast to smaller dasyurid and didelphid marsupial species, the larger dasyurid D. hallucatus species, which shows complete male die-off after mating, do not display elevated corticosteroid levels.…”

“…Together, these results suggest that the dysregulation of hormones of the HPG axis, those hormones that normally maintain tissue structure and function, is more likely driving semelparous species from the gene pool (Oakwood et al 2001;Woods and Hellgren 2003). However, which changes in sex hormones drive death remains to be elucidated; elevations in testosterone have been reported for dasyurid and didelphid marsupial species (Bradley et al 1980;McDonald et al 1981;Oakwood et al 2001), while there is a precipitous decline in testosterone concentrations and survivability of male R. fuscipes, which do not live long beyond the breeding season (Table 3; McDonald et al 1988b). Further research in other iteroparous species is required to validate the elevated post-reproductive dyotic signals observed in male and female sockeye salmon.…”

“…A similar adrenocortical mechanism impacting immune function has been proposed for the post-mating deaths of males from dasyurid marsupials (Antechinus stuartii and A. favipes) of eastern Australia (Bradley et al 1980;McDonald et al 1981), although in the larger dasyurid Dasyurus hallucatus, there is no evidence of elevated corticosteroid levels during male die-off (Oakwood et al 2001). These results do not however support the primacy of cortisol as the trigger of death suggested by others.…”

“…Conversely, other animals such as semelparous salmon and dasyurid marsupials have short post-reproductive lifespans comprising <1-4% of their total longevity (Table 1). Indeed, both female and male semelparous salmon die rapidly after their reproductive episode is complete (Truscott et al 1986), as do certain semelparous male dasyurid marsupials (Braithwaite and Lee 1979;Diamond 1982;Dickman 1993;Fisher et al 2006;Humphries and Stevens 2001;Oakwood et al 2001;Woolley 1966), polychaetes (Lawrence and Soame2009), and insecta (Fritz et al 1982). These differences in postreproductive lifespan and total longevity are related to the survival strategies of different species (i.e., requirement or not, for post-reproductive care of offspring, transfer of survival knowledge, optimal mate selection or mating strategy, optimal sperm selection/competition).…”

Fire impacts recruitment more than survival of small‐mammals in a tropical savanna

“…When no individuals were captured in a trapping occasion we logically fixed recapture and survival parameters to zero. This occurred in the male northern quolls dataset due to their semelparous life history (i.e., annual die-off of all males in September and November each year) (Oakwood et al 2001).…”