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Semelparity has been demonstrated in males of several species of Australian dasyurid marsupials. Although semelparity also has been reported in some species of neotropical didelphid marsupials, no study has conclusively demonstrated its occurrence based on survival rate estimates from field studies of marked individuals. In this study, we demonstrate that the survival rates of males of a Neotropical didelphid marsupial, the Brazilian gracile mouse opossum (Gracilinanus microtarsus), decrease sharply after the beginning of the breeding season in a cerrado remnant. However, mortality of the males after mating is not complete and a small percentage of them may survive to breed again in a 2nd breeding season. Examination of the demographic data presented here conclusively demonstrates that G. microtarsus is best described as partially semelparous.
Key words: capture-mark-recapture, Didelphidae, life history, stress
Semelparity, as defined by Cole (1954), is the condition in which reproduction occurs only once in a lifetime followed by death and leads to discrete, nonoverlapping generations. Semelparity has evolved independently many times and is common in plants and invertebrates, but is infrequent among vertebrates (Crespi and Teo 2002; Lesica and Young 2005; Stearns 1992). Among mammals, semelparity is rare and has been conclusively demonstrated on the basis of survival rate estimates from field studies of marked individuals and direct observations in several species of Australian dasyurid marsupials of the genera Antechinus and Phascogale (Bradley 1997, 2003; Braithwaite and Lee 1979; Cockburn 1997; Krajewski et al. 2000; Wood 1970). In these species, there is complete mortality of males after mating, whereas females survive to reproduce in a 2nd or even 3rd breeding season (Bradley 1997; Wood 1970).
Although the complete mortality of males after mating is obligatory in certain species of Antechinus and Phascogale, detailed studies of other dasyurid species have produced evidence for spatiotemporal diversity and plasticity in male postmating survival. For example, in island populations of Parantechinus apicalis (Dickman and Braithwaite 1992; Mills and Bencini 2000), a small, variable fraction of males in the population can survive to reproduce after the 1st breeding season, with male postulating survival apparently being mediated by varying levels of resource availability (Wolfe et al. 2004). In yet another species, Dasyurus hallucatus, complete male postulating mortality occurs only in some populations and in some years in...