Offspring sex and maternal effects influence the development and natal dispersal of an arboreal marsupial

Abstract

Natal dispersal is influenced by many environmental and biological factors and can be a time of elevated mortality risk. We aimed to understand how physical, behavioral, and demographic traits of mothers and juveniles influenced natal dispersal by studying a population of brushtail possums (Trichosurus vulpecula) reintroduced to their former range. We used radiotracking and trapping to intensively monitor the growth, survival, shelter use, and movement of juveniles and their mothers from pouch young to adulthood over a 22-month study period. We recorded multiple dispersal movement phases, with males undergoing more phases than females (6 versus 4) and dispersing 16 times farther. Dispersal age was positively related to maternal body mass for males but not females. Mothering behavior varied with offspring sex, with mothers tending to shelter daughters in a higher proportion of new shelter sites compared to sons. Females matured at a younger age and mass than males, and possums that left their mother at an earlier age reached sexual maturity earlier, regardless of sex. The timing of dispersal by males was not influenced by body mass, age, sexual maturity, rainfall, or the age of their younger sibling. Survival of juveniles (63%) was not related to sex or dispersal phase but instead sexual maturity, suggesting an effect of experience. Sex, maternal effects, and an interaction between the two influenced the development and movement of juvenile possums, suggesting that at least some sex-related differences in natal dispersal may be influenced by the mother rather than simply being the innate behavior of offspring. Although sex effects on dispersal have been reported in marsupials, the interaction with maternal characteristics has been previously overlooked.

brushtail possum, male-biased dispersal, maternal effects, mothering behavior, natal dispersal, predation, reintroduction, sex-bias, survival