A TEST OF SEMELPARITY IN THE LONG-TERM POPULATION MONITORING OF THE MARSUPIAL Marmosops incanus (DIDELPHIMORPHIA, DIDELPHIDAE)

Abstract

Semelparity, the life-history strategy characterized by death after first reproduction, is restricted in mammals to only two marsupial families, Dasyuridae in Australasia and Didelphidae in the Neotropics. Among didelphids, studies suggest a semelparous pattern for mouse opossums of the genus Marmosops. These studies have revealed that both sexes may have low survival rates after reproduction in two distinct Atlantic Forest populations. However, the semelparous strategy, which is usually considered a speciesspecific trait, can also be found in only some populations of Dasyuridae species. Thus, in this study, we aimed to investigate the occurrence of the semelparous life strategy in a population of M. incanus in an Atlantic Forest area of the PARNA Serra dos Órgãos, Rio de Janeiro, Brazil, through survival estimates using 13-year capture-mark-recapture data from a long-term population study. We established cohorts, grouping the capture histories of individuals born by the end of the breeding season. We built a global model in which survival and recapture rates vary with time and between sexes, in addition to the interaction between these factors. Model selection and averaged survival estimates were in accordance with the semelparous strategy for this population of M. incanus, with survival being affected by both sex and time. Even though we found that the survival of females was higher than that of males as expected, the difference was small. Here we confirm that another population of M. incanus displays a semelparous life-history strategy, supporting previous considerations of museums specimens. Nonetheless, the causes and mechanisms of semelparity in didelphid species are still to be understood.

Ecology of Tropical Forest Small Mammal Populations: Patterns and Process Revealed by the Longest Long-Term Monitoring Study in Brazil

“…Most marsupials are iteroparous, i.e., reproduce more than once in a lifetime, and seasonal reproducers, except for M. incanus. The low survival rate of males after the mating period supports the hypothesis that M. incanus is semelparous, i.e., reproduce only once in a lifetime (Zangrandi et al 2023). After mating, females live longer to rear their young, and only few survive to a second year (no recorded reproduction), which explains the high population turnover for this species in the study area (Zangrandi 2011).…”

Ficha de Marmosops incanus

“…Observações sobre a população Reproduzem-se durante a estação chuvosa (Fonseca & Kierulff, 1989;Passamani, 2000), entre outubro e fevereiro (Macedo, 2007). São semélparos (Zangrandi et al, 2007) todos os machos adultos morrem após o período reprodutivo, de forma que de fevereiro a agosto não há machos adultos na população; as fêmeas adultas vivem um pouco mais, não havendo fêmeas adultas na população entre junho e agosto (Lorini et al, 1994); a espécie parece apresentar uma história de vida incomum, baseada em apenas um evento reprodutivo na vida de cada indivíduo (Lorini et al, 1994). A longevidade dos machos é de um ano e das fêmeas, de um ano e meio (Lorini et al, 1994).…”