RANK AND REPRODUCTION IN COOPERATIVELY BREEDING AFRICAN WILD DOGS - BEHAVIORAL AND ENDOCRINE CORRELATES

African wild dogs (Lycaon pictus) live in cooperative packs with a cle ar-cut dominance hierarchy in each sex. Reproduction is largely monopo lized by the dominant male and female. Alpha females produced 76% of a ll litters in the Selous Game Reserve and 81% in Kruger National Park. Only 6-17% of subordinate females gave birth each year, compared to 8 2% of dominant females. In nonmating periods, subordinate females had higher estrogen levels and higher estrogen/progestin ratios than alpha females, apparently preventing ovulation. During mating periods, subo rdinate females had lower estrogen levels than dominants, mated less o ften, and were less aggressive. Subordinate males mated at low rates, were less aggressive than dominants, and had lower testosterone levels . Beta males were similar to alpha males behaviorally and hormonally, suggesting that alpha males may share paternity with beta males. If pa ternity is more evenly shared than maternity, then subordinate males h ave a larger incentive than subordinate females to remain in the pack. Following this expectation, dispersal in Selous was female biased (49 % versus 24% dispersing annually). Perhaps as a result of mortality as sociated with dispersal, the adult sex ratio was male biased, although the pup sex ratio was unbiased. In Kruger, neither dispersal nor the adult sex-ratio was biased. Reproductive suppression is widely thought to be caused by social stress in subordinates, but basal corticostero ne levels were higher in dominants than in subordinates.