Inclusive fitness and reproductive strategies in dwarf mongooses

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Abstract
Dwarf mongooses (Helogale parvula) are small, communally breeding carnivores found in woodland and tree-savanna throughout Africa. Within a pack, socially subordinate mongooses do not normally breed, yet they invariably participate in all aspects of parental care. The primary alternative to tolerating reproductive suppression is dispersal, which shortens the wait for dominance and breeding. Here, we calculate the annual inclusive fitness payoffs to the dispersing and nondispersing strategies for males and females of ages one to seven, using data from a 14-year study in Serengeti National Park, Tanzania. Factors with effects on inclusive fitness included relatedness to pack mates before and after dispersal, the effect of help on recipients' reproductive success, the probability of dispersing successfully, the probability of attaining dominance, and reproductive success after attaining dominance. All of these factors differed between male and female dwarf mongooses. We compared the contributions of direct and indirect fitness to the total fitness of mongooses pursuing each of the strategies, across a range of ages. In our population, dispersal and nondispersal both yielded direct and indirect payoffs at most ages. For dispersers of both sexes, direct fitness was the primary component of total fitness but indirect fitness was substantial for young (< 2 years old) dispersers. For nondispersers of both sexes, indirect fitness was the major component of total fitness among young mongooses (up to 2 or 3 years), but direct fitness was the major component among older mongooses. By comparing the inclusive fitness payoffs for the two strategies, we determined the range of ages at which dispersal should be favored for each sex. These comparisons correctly predicted that males should be more dispersive than females at all ages, and that males should disperse over a broader range of ages.

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