Oral presentation- Open Session 12th International Mammalogical Congress

Which life-history variables have the greatest potential contribution to population growth rate? A test with marsupials (#292)

Mariana S Ferreira 1 , Marcos Figueiredo 2 , Marcus V Vieira 2
  1. Veiga de Almeida University, Rio De Janeiro, Brazil
  2. Ecology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil

Life histories of mammals vary along a fast-slow continuum. Mammals with fast life histories mature early, have large litters, and short life spans relative to mammals with slow life histories. Differences in life history have been linked to differences in the pattern of potential contribution of survival and reproduction to population growth rate (PGR). The eutherian pattern asserts higher potential contribution of age at first reproduction and fertility to PGR in fast mammals and higher potential contribution of  juvenile and adult survival in slow mammals. However, eutherians and metatherians diverged in several aspects of their biology and ecology over the last 160 Myr. These differences reflect on the life history of the group and we hypothesized that marsupials do not follow the eutherian pattern of potential contribution. We measured the potential contribution of five variables to PGR in 17 species (26 populations) of marsupials with contrasting range of body sizes and life histories. Marsupials do not follow the eutherian pattern of potential contribution. Fertility was not an important variable for marsupials and juvenile survival had a great potential contribution to PGR no matter the life-history strategy adopted. Differences probably rely on the mode of reproduction. Fast species raise large litters which are highly vulnerable during weaning and juvenile phases. The low survival reduces female net reproductive rate and the actual number of young entering the population is similar to litter size of slow species. Thus, survival of young through weaning and juvenile phases is critical for marsupials.