Inclusive fitness and reproductive strategies in dwarf mongooses

Dwarf mongooses (Helogale parvula) are small, communally breedingcarnivores found in woodland and tree-savanna throughout Africa.Within a pack, socially subordinate mongooses do not normallybreed, yet they invariably participate in all aspects of parentalcare. The primary alternative to tolerating reproductive suppressionis dispersal, which shortens the wait for dominance and breeding.Here, we calculate the annual inclusive fitness payoffs to thedispersing and nondispersing strategies for males and femalesof ages one to seven, using data from a 14-year study in SerengetiNational Park, Tanzania. Factors with effects on inclusive fitnessincluded relatedness to pack mates before and after dispersal,the effect of help on recipients' reproductive success, theprobability of dispersing successfully, the probability of attainingdominance, and reproductive success after attaining dominance.All of these factors differed between male and female dwarfmongooses. We compared the contributions of direct and indirectfitness to the total fitness of mongooses pursuing each of thestrategies, across a range of ages. In our population, dispersaland nondispersal both yielded direct and indirect payoffs atmost ages. For dispersers of both sexes, direct fitness wasthe primary component of total fitness but indirect fitnesswas substantial for young (< 2 years old) dispersers. Fornondispersers of both sexes, indirect fitness was the majorcomponent of total fitness among young mongooses (up to 2 or3 years), but direct fitness was the major component among oldermongooses. By comparing the inclusive fitness payoffs for thetwo strategies, we determined the range of ages at which dispersalshould be favored for each sex. These comparisons correctlypredicted that males should be more dispersive than femalesat all ages, and that males should disperse over a broader rangeof ages.