Semelparity in a population of Gracilinanus agilis (Didelphimorphia: Didelphidae) inhabiting the Brazilian cerrado

Although reproducing once in a lifetime (i.e. semelparity) is considered rare among vertebrates, it has evolved at least five times in two distantly related marsupial families; the Australian Dasyuridae and South American Didelphidae. The major aim of this research was to describe the population dynamics, reproductive strategy and associated life-history traits of the agile gracile mouse opossum, Gracilinanus agilis, in order to position the species along the fast-slow life-history continuum. Sampling was carried out through mark-recapture, from August 2010 to April 2013, in a Brazilian area of cerrado. Reproductive activity was seasonal and synchronized among females, and occurred from July to January/February. After mating, population size decreased due to male disappearance, which seems to be explained by post-mating male die-off. Phylogenetic predisposition toward semelparity in Gracilinanus lineage and intense competition for females may contribute to male die-off, as indicated by several evidences such as male-biased sex ratio, signs of aggression in reproductive males, and a pronounced gain in male body mass and size prior to mating. Although two litters were produced, most females disappeared after weaning their young, indicating post-reproductive senescence and resulting in discrete, non-overlapping generations, characterizing semelparity in this population of G. agilis.