Cooperative Fish and Wildlife Research Units Program: Idaho
Education, Research and Technical Assistance for Managing Our Natural Resources

1. Breeding opportunities are inherently limited for animals that live and breed in groups. Individuals use various strategies to secure breeding positions in such populations ranging from inheritance within their group to dispersing to an existing group or establishing a new group. Turnover in breeding positions can have marked effects on groups of cooperative breeders, particularly social carnivores.
2. We generally know little about how breeding vacancies are filled and what factors might influence an individual’s ability to successfully fill a vacancy.
3. I used data from gray wolves to ask whether breeding vacancies were filled by individuals from within groups or by adoptees from outside the group. I hypothesized sex, group size, and genetic relatedness would influence how breeding vacancies were filled.
4. Across 37 breeding vacancies, females were three times more likely than males to inherit breeding positions within their group. Group size did not influence whether a breeding vacancy was filled by an adoptee or inherited by an individual from within the group. Genetic relatedness, however, was 30% higher in groups when females were adopted into breeding positions than when they inherited breeding positions from within groups.
5. Female wolves appear to bide their time waiting for a breeding position thus, they may be expected to show more helping behavior than males in their natal groups. Increased body size can be advantageous for males to secure a breeding position in a new group thus, males may act selfishly and consume more food and provision pups or help less in their natal group. Dispersing and monopolizing a breeding position is not the only avenue to increased fitness, however. Male wolves can also gain fitness benefits from extra-pair paternity while waiting for breeding vacancies to open elsewhere as has been observed in this population. Because of their strong reliance on dispersal to secure a breeding position, male wolves appear to be the primary vector promoting genetic diversity in populations of gray wolves.